You can invent a character.

I have been tempted to work with a sort of half Willa Ford, half Jessica Simpson character... someone young, richer than she's ever been, who has to be taken care of by handlers or she'll be broke and without a career.

Girls HATE Willa Ford with furious passion, and I find that really interesting. (When you have a fledgling music career and only a bad pop song to your credit, do NOT name drop sleeping with a Backstreet Boy.)

Jessica Simpson seems to be dumb, but she's one of the shrewdest, slyest cats I've ever seen, so that's kind of inspiring, too...

NICK: "Can I get a Hummer?"
JESSICA: (confused look) "You mean the car...?"
NICK: (embarrased) "Uh, sure."