NEW YORK - Beyonce Knowles says she becomes someone else when she's onstage, an alter ego she's even given a name to: Sasha. "I wouldn't like Sasha if I met her offstage," the 25-year-old singer-actress tells Parade magazine in its Dec. 17 issue.

"Oh, no. She's too aggressive, too strong, too sassy, too sexy! I'm not her in real life at all. I'm not flirtatious and super-confident and fearless like her."

"I created my stage persona to protect myself," she says, "so that when I go home, I don't have to think about what it is I do. Sasha isn't me. The people around me know who I really am."

One of those close confidantes is her boyfriend, music mogul Jay-Z. "When I'm in love, I'm there 100 percent," she says. "But if I don't trust someone, if I'm not totally there because of it, then I'm not going to waste my time."

Knowles, who started out in the girl group Destiny's Child, plays singer Deena Jones opposite Jamie Foxx, Eddie Murphy and Jennifer Hudson in the movie musical "Dreamgirls," opening Friday.

She's also nominated for four Grammy awards, including best contemporary R&B album ("B'Day") and best female R&B vocal performance ("Ring the Alarm").

Life wasn't always so good, though. In 2000, two members left Destiny's Child and sued her manager-father Mathew Knowles, claiming conflict of interest in his management. The case was settled out of court.

"It was tough," she recalls. "Before that, the media didn't pay attention to me personally. It was just our music. After that, I felt attacked. The way people reacted was different. My privacy was over.

"I went through depression. I didn't eat," she continues. "I stayed in my room. I was in a really bad place in life, going through that lonely period: `Who am I? Who are my friends?' My life changed."

She knows there are changes ahead, too.

"I think about the future, about what my life will be like when people are tired of my songs and movies," she says. "I'll still want a life then, beyond the music. Maybe I'll teach or mentor at a Boys & Girls Club. I want to have a family. I want to be happy."