I would just let it go personally, but you asked for methods of madness not a morality lesson so...

She's stuck up so I'm going to take a guess mommy and daddy bought her a REALLY nice car that she loves. A pound or two of sugar in the gas should take care of that. If you don't want to be quite so mean, just let the air out of the tires. Peanut butter (and the like) can be put under the door handles. Painting fuck off in paint stripper on the hood could also be intersting. Also it should be noted shoe polish is notoriously hard to get off of car paint (or anything else for that matter).

An electric razor can work wonders if you take out chunk of hair right down (or at least close) to the scalp. Hard to be posh and stuck up with a large bald spot.

Itching/burning powder/spray is always a winner. Works best in shoes/undewear/etc. If you have access to her locker, thats the best place to go to work with this stuff.

Starting rumors is always a classic.

Of coarse if you have lots of skill and really want to stick it to her. Just have sex with her mom, and make sure she knows.

Again though, I'd say just leave it be. If she is a bitch, everyone knows it anyways, no need to go through extravagent measures to prove it to the world.