I think it's because at the basest of levels, all women hate each other. They can cover this up at times by shopping our going out for drinks together, but that's just until they're out with a different "friend" and then the favorite activity turns into completely eviscerating the first "friend". Wash, rinse, repeat.
So my question is, why should you care? Yes, this one has an attitude, has yet to mature past the listening to emo music stage, and is probaby guilty of most of the things that the other posters have accused her of as evidenced by her refusal to acknowledge the time-honored woman tradition of only being snarky to another woman
behind her back. All that means is that there's one less person in class that you have to play that "oh my gosh, how are you today!" small talk game that's interrupted with those overcompensating fake laughs that sound nothing like your real laughs because you're both way too concerned with making the other person believe that you don't actually hate her guts. And of course, as mentioned before, you also have a new target for cunt punts. I see no real downfall here.
P.S. I'm kidding.
Kind of.