How do deal with a certain girl at school?

I'm not usually the type of person to ask a question like this, but I can't handle it anymore. So, this girl (let's call her 'Amy' ) and I were friends in 5th grade but went our seperate ways in middle school. This year she's in a few of my hours, and she's outrageously two-faced. She's decently nice to me up front, but you can tell she thinks I'm weird because she just glares at me sometimes when she thinks I'm not looking (THAT sounds rather strange). Usually with her little popular cronies. But around three months ago, my trustworthy male-friend (let's call him 'Alex') told me she was calling me creepy and emo in his 5th hour, by a couple others, one of them someone I'd considered a friend. I was pretty sad (mostly because of the person I'd considered a friend was contributing) but I got over it. But, I still don't really talk to her. Soooo now I have to work with her for a final project, and she just starts whispering in her friend's ear and looks at me. The irony of this is her friend is the one she talks about most behind her back. I may just be paranoid, but some grudges never die. So, if this should continue, what should I do? I would love to punch her, but that's not the wisest thing to do.