What do I do with a girl like her?

There's a new girl at my school, Rebecca. My group of friends and I hate her for "feeling close"; it's beyond irritating. One time, I was looking at pictures of my favorite boy band on one of my best friend's iTouch and Rebecca was all, "Whose is that? Is that yours?" I ignored her but in my head I was thinking, "CAN'T YOU SEE I'M BUSY?!" And then there was another incident... I was listening to songs on my phone's music player and suddenly Rebecca asks, "Can I look at your phone?" while trying to grab it before I could even permit her to look. I held it with all my might and sternly said no but I really wanted to smack her hand. (MAYBE I would've allowed her if she didn't do what she did.) Just recently, two more incidents happened: a) I was being canorous (but not a kiss a$$) towards my teacher and hugged her then suddenly Rebecca comments in public that she can see my underwear. (I mean, WTF. Why was she even looking there?! Luckily my seatmate defended me.) b) She was poking fun at a clmate of mine and Rebecca was enjoying it but when I gave her a taste of her own medicine, she was a sore loser. (She hasn't bothered me since then so far.) Oh, and she often crashes in the high school senior's clroom during recess or lunch and sometimes prolongs her stay even when the bell has rung. (Is this even her clroom? I don't think so.) I'm trying my best to remain cly and exhibit grace under pressure but she's really trying my patience. The only things stopping me from laying a finger on her are that I don't want to risk suspension or expulsion or earning the reputation of a bully. Honestly, I hate her so much that I've mentally "double murdered" her. In fact, if I were her, I'd fear the day I get a driver's license because I'd gladly run over her once I do. That's how much I hate her.