LONDON -- Ashlee Simpson collapsed onstage again on Monday night, during her theatrical debut at the Cambridge Theatre in the West End. But this time it was on purpose. As Roxie Hart, the lead in "Chicago," Simpson was playing a character who works the media: To gain attention and sympathy for her upcoming murder trial, she pretends she is pregnant and faints. Roxie's coverage returns to the front pages, and she gets off.

While the producers of "Chicago" could rightly be accused of pulling a little stunt of their own -- casting a notorious lip-syncher to do live theater -- it too worked. Despite her previous live mishaps, Ashlee turned in a nearly flawless performance, converting some haters into believers, at least in London.

(Click here to watch Ashlee onstage in London, on Overdrive.)

"Earlier today, I was a little bit nervous," she said after the show, "and then I put on a show for my family. They came to my dress rehearsal, and then the nerves went away. It was more like happy little butterflies."

Her father, Joe Simpson, said it was actually the other way around. "I think she was more nervous about performing in front of her family than in front of a crowd," he said. "She was nervous all day. She was afraid. 'Am I going to make it?' So we just got that out of the way."

"I try my hardest not to read [all the criticism], but it's obviously around and in your face," Ashlee said. "My family, my mother especially, taught me to be a fighter, and that's the thing Roxie is: She always finds a way to pick herself up."

Maybe it's the role Ashlee was meant to play. Roxie is by no means a pro -- she's a wannabe vaudeville act who desperately wants to be famous, and through circumstances unrelated to her talent (or lack thereof), she becomes a star. Roxie's actually disappointed at the end of her trial when the media move on to the next case. Her manipulative lawyer, Billy Flynn -- currently being played on New York's Broadway by Usher -- points out that she got away with murder, that he saved her from the noose, but she's fixated on the fact that nobody wants to take her picture anymore. Ashlee says she found enough of Roxie in herself to make the part her own.

"Roxie's a fun character to play," Ashlee said. "For me, it wasn't like I ever wanted to have my name in the papers. It was usually like, 'Oh, no!' But I know what the feeling is. And I know what the celebrity life is like, so I tried to bring a little comedy to that."

It was more than a little comedy -- audience members after the show described the singer's take on Roxie as the funniest one they'd seen, mostly because Ashlee was so physical with her performance. She contorts her face, pushes up her breasts with pads and gives her co-stars the raspberry -- all the little things that add up to a Roxie who is both child and woman. She's a character who's caught between needing the parental guidance her lawyer and prison warden provide and rebelling against them at the same time. Ashlee's Roxie is sexy and stupid, knowing and naive, all at once.

"She's the youngest Roxie we've ever had, and she just has certain qualities that make the role so delicious," "Chicago" producer Barry Weissler said. "The lines and the steps and the blocking and the songs are all the same, but because of her personality, it's different. Her beats are different."

"You get to act out a lot with your body in theater," Ashlee said. "You have to be sharp with your movement and whatnot. It's silly and out there, which is nice. It's kooky."

"I think Ashlee made Roxie who she wanted to make Roxie [into]," her sister Jessica said. "It was her stage tonight. She was brighter than the lights. She was it. My girl!"

"This was just the opening night," Ashlee said. "I'm excited to see what the rest of my five weeks onstage will be like."