Gossip Girl was brilliant for putting their version of this character in a pilot catfight with the hot girl next door. That's what every male audience member secretly wants and scribbles furiously about in their fan fiction, anyway, so why not give it to them?
Though they may not always be front and center, it's important to have a bad girl, easily identified by her leather jacket, fierce red make-up, and/or tendency to show a little more skin than her fellow classmates. This is a hard part to get right, as the character can't simply be bitchy. That would work just fine in a movie, but there's a march towards syndication to get through here. With that in mind, she must have a tough home life or some other justification for using her looks and queen bee status as a coping mechanism.