A weird girl is coming back to my school Help?

Well Me and this girl named Tracy were just friends not best friends just friends. And she thought I was like the best thing ever I guess she would follow me and talk to me all the time. It got VERY annoying. I mean I was nice to her and all, but everyone else wasn't. So she changed schools. I mean I tried my hardest not to talk to her while she left, I was trying to make her forget me. But she didn't She tried to add me on Facebook like 8 times, So finally I accepted. Now she annoys the heck out of me, but I keep my cool. She is trying to be all cool by dying her hair black and wearing boy cloths. She was a out cast already when she went to my school, but now she's coming back. I have changed, I used to be a tomboy but that phase is long gone.... I am afraid she will follow me everywhere and people will treat me worst then they already do. I don't want you guys to think I hate her, It's just that she wants to be like me so bad I hate it. She is coming back the 18th. So that gives me little time to prepare. WHAT DO I DO?? She is going to sit by me at lunch and follow me and ugghhh :( Help me!!