In "Mean Girls," there is one character worth playing, and it's Regina George. I can't help but wonder, if Lindsay Lohan had insisted on playing Regina, might her career have unfolded in a different way? My favorite moment in the original film is when Regina observes that Cady looks pretty in a certain shirt. Cady shrugs and offers thanks. This is a major sin: The correct response would have been a needy, whiny kind of protest. ("Omigod, I look SO AWFUL!") Regina seizes the moment: "You agree with me? You personally think that you look pretty?" (Calculations are occurring in Rachel McAdams's brain.) A new anthem, co-written by Renee Rapp, imagines what Regina might say to a protege. Regina puts herself in the shoes of her audience, reciting her frenemies' questions: Where she at? What's she doing? Who's she with and where's she from? Oh, she's this. Oh, she's that. She's a flight risk on the run. She's back... S...