I have this female friend. Known her about two years now. About 4 months ago her attitude shifted completely and to put it bluntly, she's changed to a total bitch. To explain this a bit, she doesn't like any of my friends that I sit with at lunch. These friends I've known longer than her. I really don't understand her logic here but when she acts bitch towards them, she expects me to defend her and back her up. None of my friends have ever done anything bad to her or gave her a reason to act as she does. That's not all. About every other day she finds a reason to bitch at me and I'll just be sitting there doing absolutely nothing, which leads to me to ask her to stop being "bitchy" and then gets mad, calls me an ass, then leaves me alone for the rest of the day. Then the next day, she acts as if nothing even happened. And apparently whenever I have food, I'm under the obligation to share it with her and gets pissed off at me if I don't. This isn't just a "once-a-month" thing either because it happens way too frequently and it has been for the past 4 months. Like today, she kept talking, I buried my face into a book, but then she started playfully kicking me. I asked her to stop and she wouldn't. 10 minutes later of putting up with her poking at me, she called me an ass and left me alone.
Essentially, I'm at a very stressful part of my school career, and having to deal with her everyday is increasing my level of stress which I don't need. I don't want to be friends with her anymore because of the way she treats me and my friends. I've tried several things and none of which are working. I've tried ignoring her, but she's one of those people who will keep talking if she notices you're not paying attention to her. I've tried intentionally acting like an ass towards her in hopes she'll leave me alone, but again, the next day its like her previous day was completely erased. I've asked her to leave me alone and I've even told her I don't want to bearound her. I've told her why. Yet the next damn day, she's right there being an attention whore around me. I'm basically here asking for advice on how to solve my problem.