Like her big sister, Jessica, Ashlee Simpson is branching out from pop music to movies. She makes her big-screen debut in "Undiscovered," a music-filled drama about young people with dreams of reaching stardom in Los Angeles.

The 20-year-old Dallas native plays Clea, an aspiring actress who sometimes sings with a band at an L.A. club. Her character is the supportive friend of the film's leads, aspiring rocker Luke Falcon ("Sky High's" Steven Strait) and model-turned-actress Brier Tucket ("Broken Flower's" Pell James). The film also stars Carrie Fisher, Peter Weller and Kip Pardue.

Simpson says that living in L.A. helps her to relate to the movie. "I've had my fair share of struggles going from label to label and being turned down," she says. "It's hard. You have to find your unique sound (and) your own unique way of acting, whatever it may be."

The actress/singer's father and manager, Joe Simpson, is one of the executive producers, so she gets plenty of screen time and performs the title song (which appeared on her debut album, "Autobiography").

"I didn't write the songs I sing in the movie. So it was kind of hard for me to step out and do something that wasn't my music, but it was a lot of fun," says Ashlee Simpson. "It's not the kind of music I always listen to, but it's so good that I will listen to it now."

In person, Simpson's green eyes are luminescent. Her hair is newly dyed Harlow gold, short and wavy (in contrast to her usual straight brunette). She is stylishly dressed in a lacy, see-through blouse, black crop pants and boots.

But being a blond isn't more fun, Simpson says, she has fun no matter what, despite being single. Perhaps that will change when she turns 21 on Oct. 3.

Flanked by publicists, she appears to be optimistic about the future. But she's still recovering from that embarrassing "Saturday Night Live" gaffe last fall in which Simpson stopped singing during a live performance, then did an impromptu hoedown while her pre-recorded voice kept on going. Jokes and accusations of lip-synching followed.

"I've had a lot of lessons learned this year. The biggest learning experience was probably 'SNL' and how to pick myself back up and keep at it. ...Which goes to say that even when you do have success, there are still struggles. I really like that they get that message across in the movie," Simpson says.

The singer recently completed her first headlining national tour, returned to the recording studio and is set to release her sophomore album, "I Am Me," this fall. She says that some of the songs have a slightly different sound.

"I went back to the same producer, John Shanks, because we work really great together. There are some (songs) that will remind you of the last album, but I've grown up a lot lyrically, vocally, everything."

And although Simpson has caught some heat for some of the lyrics on her upcoming single, "Boyfriend," she stands by them, explaining: "It's just a funny line: 'I didn't steal your boyfriend.' It's a song every girl can relate to.

I'm sure everybody thinks that at some time someone stole their boyfriend. I write from the heart, so I don't worry about what people think."