How do I end this 'friendship'?

Over the 2009 summer, I was forced to move to Virginia. Now I'm spending my senior year in a school I'm not familiar with, with people who don't understand that I like being alone. For example, at. My old school, people understood that I liked to chat and joke in class, but outside of it, I preferto be alone. These people do NOT comprehend this, and there's no place to go on campus to giveme my seperation time (I am VERY introverted). I could stand all this if it weren't for this one girl. From day one, she wouldn't stop bugging me. She thinks of me as her best friend, though I want her to leave me alone. I thought she would get the hint when I constantly told her how busy I was, but she won't give up. I get really embarrassed when it comes to confrontation, so sometimes I just give in. It's now February and I STILL can't stand her. How do I get her to leave me alone? Here's what bothers me the most:
She seems really popular, but she only hangs with me
She's a beauty pageant queen, so she's obsessed with being skinny. There's not one day she won't say "ugh, I'm so fat. Anything over a size 5 is fat." Note: i'm a size 12. She knows this and saysit anyways.
She gets angry when anyone calls her on her cheating on her once fiancé and boyfriends
I'm pretty sure she only talks to me bc I'm a light skinned black girl (she says things that raise brows and give that Impression. Also will always take a chance to touch my hair. This only happens to me with black girls).
She's so NEEDY. It gets to the point where she'll ask me a question just so she can turn the conversation to her. I have had to engage in hour long talks about all her good points. And she does that obnoxious, not to mention childish, thing where she says "oh, I'm so bad/ugly/stupid" so everyone will jump in and say otherwise.
She keeps asking about my grades when I say I don't feel comfy telling. Shoves hers in my face anyways
laughs at her own jokes?
She also wears shirts that allow wardrobe malefunctions and keeps getting more intricate tramp stamps.
Maybe i'm judgemental, but she's an attention who re. She needs me to constantly feed her ego. Ihave to sit next to her for two hours every other day (damn Virginia schooling), so I want to get away from her without awkwardness. Is it possible? ?