What is going on

Sounds like she may not know what she wants... She maybe insecure about relationships or feels pressured in some way.... and at the same time she may really like you? Don't take what I say as a deffinate answer, but if shes feeling jumpy then it sounds like she doesn't know what to do with herself... I dont think shes playing games because otherwise she wouldn't have much of a reaction when she see's you in school. Maybe try talking to her? Because either way its not fair that she keeps leading you on in that way...

Honestly I am the same way around guys whether I am romantically interested in them or not. I am horrible around guys I get intimate with just because I don't know how to act or deal with the situation. I think I have intimacy issues, I don't know how to communicate with guys after I kiss them etc etc. She probably just doesn't understand what she wants and doesn't know how you feel about it either. I would honestly just make a lot of effort to talk to her like a friend and make her feel as comfortable as possible. Maybe attempt initiating kissing later on as well? just try to make her feel less anxious around you. If she's comfortable around you, she'll talk more and then you'll be able to figure her out, what she's thinking etc.

She sounds exactly like me right now with this guy I like. I know I acted like that after I felt like I got too close to him too fast. The idea of a relationship basically scared the hell out of me and I pushed him away, and although other factors have taken him away from me as well, I've regretted it constantly ever since. I'm not saying this is 100% the case, but if it is, give her some time but don't give up on her.