How very nice of you to come," Hallee Hirsh greets a visitor to her suburban Los Angeles house. "May I bring you a soda? A snack, perhaps?"

Can this mini-Miss Manners really be Rachel, the rebellious daughter of ER's Dr. Mark Greene? Or the delinquent who fed lye to a cat on Law & Order and shot her stepdad on Judging Amy? The same. Not to worry though. "No matter what nasty little role I might have," says Hirsh, 14, "it's still me inside."

The real "me" turns out to be the sunny-tempered, home-schooled daughter of military officers—retired Marine Lieutenant Colonel Mike, 54, and Navy Captain Deborah, 47—who prefers golf to Rachel's penchant for tearing down street signs with her druggie boyfriend. "We took this bubbly girl," says ER co-executive producer R. Scott Gemmill, "and said, 'We have to turn you into a terror.' "

Hirsh got turned on to acting as a toddler when her brother Greg, now 20 and a film student, took drama lessons. "I yelled, 'My turn!' " she says. Soon she was on soaps (Loving, All My Children) and costarring in 1998's You've Got Mail. "We were afraid she'd only be cast in nice-girl roles," says Deborah. But after her chilling '99 guest turn on Law & Order, "a woman came up to me and said, 'I wanted them to put you in jail and throw away the key!' " says Hallee. "My dad said that was the best compliment I could get."