Girls!!!! plz help...why is she playing me?

First, were both 15 told her I liked her through text but never made a move because she didn't say anything, she would barely talk to me but would smile at me whenever I looked at her, I also overheard her talking about her break up with her mysterious bf over the weekend which is the same weekend I had told her I liked her...this went on for a week, then she completely ignored me and started flirting with other guys in front of me to piss me off... This went on for a month...thenly one day we had a small conversation and she had insisted that I would join her griup for her ignmentthen one day she randomly texts me if I can help fix her phone which I did, then,the next day, she got this guy...she kissed him in front of me and she knew she was hurting me and she just come up to me like nothong happened and tells me what had happened to her phone, and they weren't even officially going out, then that same day.... She kept trying to talk to me by rubbing her hand all the way down my arm, she also starts calling me by my nickname, which she had made up but then taken away during that period of being a *****...my teach took my drum sticks away and she just yells out 'awww poor jorgie'...I tried ignoring her but she just got pissed and said if I keep ignoring her she would delete me off her blackberry messenger....she also moved to the seat in front of me and started stretching back and putting her hair in my face....the next day they were officially going out....but then she moved to the seat in front of me and started doing the same hair thing and we were watcjing a movie in cl that day, so she kept turning around to ask me about the movie and I was on my phone and all of a sudden she turns around and asks me 'what are you doing' and I just reply 'what?' And she just turns around going 'nothing'.... Now she is ignoring me again....why is she acting like this.