Goodbye, Cameron Diaz, party girl. (sniff) Hello, Ms. Mature.

When a party girl goes serious, it's time to cry.

Take, for example, Cameron Diaz, the blond, blue-eyed, A-list movie star who has more often specialized in raucous comedies ("There's Something About Mary," "What Happens in Vegas") and will customarily go to any length to get a laugh (the classic hair gel routine in "Mary.")

It was only a few years ago, for a Virginian-Pilot interview, that she told us, in her joyous la-di-la style: "What are my career plans? I haven't the slightest idea. I don't make plans. What would I like to achieve? I can't think. Maybe learn to milk a cow. Hey, that's good. I'd like to milk a cow! I'm entitled to ideas like this. I'm blond."

The still-single, self-described tomboy has added to her gadabout image with a history of hot dates - (Justin Timberlake, Matt Dillon, Jared Leto).

That was then. Starting this weekend, Diaz will surprise her fans by playing a strong and determined mother who will go to any length to save her terminally ill daughter. Based on the best-selling novel by Jodi Picoult, "My Sister's Keeper" is a drama that challenges perceptions of family love and loyalty and dares to go where other movies feared to tread - directly into competition with the expected action blockbuster "Transformers."

The producers, who include Norfolk native Stephen Furst, see a chance for "counterprogramming" and they know they have a major star as a centerpiece. "At the least," one of them said, "we'll get people who can't get in to see 'Transformers.' " At the most, maybe a box office tally like other highly successful tearjerkers: "The Notebook," "Ordinary People," "Terms of Endearment." Not everyone wants to see robots turn into cars.

Sitting at the Pacific Ocean seaside resort of Casa Del Mar in Santa Monica, Calif., Diaz acknowledges that life, as well as the role, have turned serious for her in the past year. Her beloved father, Emilio Diaz, 58, died unexpectedly of complications from pneumonia during filming, requiring the production to temporarily shut down.

"He was, in many ways, the center of my life - a force that kept me grounded in the middle of all this crazy business," she said, "but I was lucky that I had this film and this cast to come back to. The role gave me somewhere to go when I needed that."

Still, she maintains she's not becoming a drama queen. "I'm pleased with the parts I've been offered in the past. I'm content to be the bubbly, happy person, not the traumatized tormented Oscar-nominated person. I've never had an acting lesson. When I read this role, I found that Sara, this woman, was someone I wanted to understand and didn't. I don't entirely agree with her choices, but I wanted to play her. It was no career choice. It just happened to be a part that was available to me."

Sara is the mother of teenager Kate (Sofia Vassilieva of TV's "Medium") who is afflicted with a rare, terminal, leukemia condition. In a desperate effort to save her, Sara and her husband (Jason Patric) genetically engineered another child to be a perfect match who could donate body parts to keep Kate alive. The younger daughter, age 11, is played by Oscar nominee ("Little Miss Sunshine") Abigail Breslin, who, in rebellion, hires a lawyer (Alec Baldwin) to seek "medical emancipation" from her parents. Sara gives up her career as a lawyer and is apparently willing to give up her younger daughter to keep the older daughter alive.

"She's very single-minded," Diaz said. "It took me a while to grasp her."

Diaz's trademark chirpy, high-pitched laugh is still there, but not as often as back when we observed her for a full weekend at The Homestead resort near the Virginia-West Virginia border. Her date for the weekend was Matt Dillon. She bowled. She rode horses. She was everywhere. He often sat quietly. He seemed much older. (He was, just slightly.) As we predicted, the relationship didn't last. Her most recent beau was model Paul Sculfor. She is still friends with all her former boyfriends.

"I think you tend to be with the right person at the right time in your life. I've been lucky that way. But then I change. They change. It's no mystery. I am a much different person than I was five years ago, but I can be happy in the present. I don't look back. I don't look forward. I grew up with a lot of boys. I probably have a lot of testosterone for a woman."

Until now, her movie fans never thought of her as a mom. What about this choice of roles?

"I knew you'd get to that soon enough," said the 36-year-old. "I know what you mean. Why play an 'older' woman? Well, I'm not 25 anymore, and I never will be. Good. I wouldn't go back to 25 if I had a chance. That's over. I think every part of life has its place. If I were a different person, I could be the mother of these two girls in the script. I have three nieces and a nephew, and I've changed diapers and all that. I don't regret that I don't have children, but then I don't count it out, either. I'm

still young. I am the person I am partially because I don't have children."

She glanced playfully at her two co-stars, Abigail and Sofia. "I'll leave the next Charlie's Angels to these two girls. Take over, girls."

Nick Cassavetes, the director, wanted her for "My Sister's Keeper" specifically because she was not known particularly for serious roles. "I didn't want an actress who would be doing what she'd done before, and besides, Cameron, I knew, was fully capable of handling this part."

In spite of her deprecation of her acting abilities, Diaz has won awards. The New York Film Critics named her best actress of the year for "There's Something About Mary" (a rare honor for a comedy role), and she has been nominated four times for Golden Globes including for "Mary" as well as "Being John Malkovich," "Vanilla Sky" and Martin Scorsese's epic "Gangs of New York" (which she regards as the high point of her career).

Born in San Diego to a Cuban father and a mother descended from Cherokees, Italians and Germans, she points out that "my Latin roots are very strong. Because I'm blond and blue-eyed, people who aren't Hispanic can't believe I am."

At 21, she tried out to be an extra in the Jim Carrey comedy "The Mask." Instead, she became the leading lady.

"At first I thought it was just some little independent thing and wouldn't even be in theaters," she said. It made her a star, and she has remained one for the past 15 years. She was only the second actress in movie history to command $20 million for a single role, after Julia Roberts.

She got $20 million each for "Charlie's Angels: Full Throttle" and for doing the voice of Princess Fiona in "Shrek 2." Currently, she's voicing Fiona again for the upcoming "Shrek Goes Fourth," which is set for release next year.

It's back to laughs.

Mal Vincent, (757) 446-2347, mal.vincent@pilotonline.com. When a party girl goes serious, it's time to cry. // Take, for example, Cameron Diaz, the blonde, blue-eyed A-list movie star who has more often specialized in raucous comedies ("There's Something About Mary" "What Happens in Vegas") and will customarily go to any length to get a laugh (the classic hair gel routine in "Mary.")

It was only a few years ago, for a Virginian-Pilot interview, that she, told us, in her joyous la-di-la style: "What are my career plans? I haven't the slightest idea. I don't make plans. What would I like to achieve? I can't think. Maybe learn to milk a cow. Hey, that's good. I'd like to milk a cow! I'm entitled to ideas like this. I'm blonde."

The still-single, self-described tomboy has added to her gadabout image with a history of hot dates - (Justin Timberlake, Matt Dillon, Jared Leto).

That was then. This is now. Opening today, Diaz will surprise her usual fans by playing a strong and determined mother who will go to any length to save her terminally ill daughter. Based on the bestselling novel by Jodi Picoult, "My Sister's Keeper" is a drama that challenges perceptions of family love and loyalty and dares to go where other movies feared to tread - directly into competition with the expected action blockbuster "Transformers."

The producers, who include Norfolk native Stephen Furst, see a chance for "counter programming" and they know they have a major star as a centerpiece. "At the least," one of them said, "we'll get people who can't get in to see 'Transformers.'" At the most, maybe a box office tally like other highly successful tearjerkers: "The Notebook," "Ordinary People," "Terms of Endearment." Not everyone wants to see robots turn into cars.

Sitting at the Pacific Ocean seaside resort of Casa Del Mar in Santa Monica, Calif., Diaz admits that life, as well as the role, have turned serious for her in the past year. Her beloved father Emilio Diaz, 58, died unexpectedly of complications from pneumonia during filming, requiring the production to temporarily shut down.

"He was, in many ways, the center of my life - a force that kept me grounded in the middle of all this crazy business," she said, "but I was lucky that I had this film and this cast to come back to. The role gave me somewhere to go when I needed that."

Still, she maintains that she's not becoming any tragic drama queen. "I'm pleased with the parts I've been offered in the past. I'm content to be the bubbly, happy person not the traumatized tormented Oscar-nominated person. I've never had an acting lesson. When I read this role, I found that Sara, this woman, was someone I wanted to understand, and didn't. I don't entirely agree with her choices but I wanted to play her. It was no career choice. It just happened to be a part that was available to me."

Sara is the mother of teen-aged Kate (Sofia Vassilieva of TV's "Medium") who is afflicted with a rare, terminal, leukemia condition. In a desperate effort to save her, Sara and her husband (Jason Patric) genetically engineered another child to be a perfect match who could donate body parts to keep Kate alive. The younger daughter, age 11, is played by Oscar nominee ("Little Miss Sunshine") Abigail Breslin who, in rebellion, hires a lawyer (Alec Baldwin) to seek "medical emancipation" from her parents. She gives up her career as a lawyer and is apparently willing to give up her younger daughter to keep the older daughter alive.

"She's very single-minded," Diaz said. "It took me awhile to grasp her."

Diaz's trademark chirpy, high-pitched laugh is still there, but not as often as back when we observed her for a full weekend at the Homestead Resort on the Virginia-West Virginia border. Her date for the weekend was Matt Dillon. She bowled. She rode horses. She was everywhere. He often sat quietly. He seemed much older. (He was, just slightly). As we predicted, the relationship didn't last. Her most recent beau was model Paul Sculfor. She is still friends with all her ex-boy friends.

"I think you tend to be with the right person at the right time in your life. I've been lucky that way. But then I change. They change. It's no mystery. I am a much different person than I was five years ago but I can be happy in the present. I don't look back. I don't look forward. I grew up with a lot of boys. I probably have a lot of testosterone for a woman."

Until now, her movie fans never thought of her as a Mom. What about this choice of roles?

"I knew you'd get to that soon enough," said the 36-year-old. "I know what you mean. Why play an 'older' woman? Well, I'm not 25 anymore and I never will be. Good. I wouldn't go back to 25 if I had a chance. That's over. I think every part of life has its place. If I were a different person, I could be the mother of these two girls in the script. I have three nieces and a nephew and I've change diapers and all that. I don't regret that I don't have children but, then, I don't count it out, either. I'm still young. I am the person I am partially because I don't have children."

She glanced playfully at her two co-stars, Abigail and Sofia. "I'll leave the next Charlie's Angels to these two girls. Take over, girls."

Nick Cassavetes, the director of "My Sister's Keeper," wanted her for "My Sister's Keeper" specifically because she was not known particularly for serious roles. "I didn't want an actress who would be doing what she'd done before and, besides, Cameron, I knew, was fully capable of handling this part."

In spite of her self-deprecation of her acting abilities, Diaz has won awards. The New York Film Critics named her best actress of the year for "There's Something About Mary" (a rare honor for a comedy role) and she has been nominated four times for Golden Globes including "Mary" as well as "Being John Malkovich," "Vanilla Sky" and in Martin Scorsese's epic "Gangs of New York" (which she regards as the epitome of her career).

Born in San Diego to a Cuban father and a mother descended from Native American Cherokees, Italians and Germans, she points out that "My Latin roots are very strong. Because I'm blond and blue-eyed, people who aren't Hispanic can't believe I am."

At 21, she tried out to be an extra in the Jim Carrey comedy "The Mask." She, instead, became the leading lady.

"At first, I thought it was just some little independent thing and wouldn't even be in theaters," she said. It made her a star and she has been a star for the past 15 years. She was only the second actress in movie history to command $20 million for a single role - after Julia Roberts.

She got $20 million each for "Charlie's Angels: Full Throttle" and for doing the voice of Princes Fiona in "Shrek 2." Currently, she's voicing Fiona again for the upcoming "Shrek Goes Fourth," which is set for release next year.

It's back to laughs.

Mal Vincent, (757) 446-2347, mal.vincent@pilotonline.com.