As Optical Ilusion said, it would be good if you gave her a taste of her own medicine, if she flirts with you but you know that she is toying with you, she is simply not worth it, sometimes girls (and guys too) can be so cruel with people that they know have crushes on them, I had this experience with a guy I liked from highschool, and in the meantime he didnt know I liked him he was nice and friendly, so I felt it was time to make my move, I sent him the message I liked him with a friend of mine, and instead of making any move -or treating me normally as saying "hey thanks but Im not interested" he started to flirt and toy with me (then he ignored me and so on I was pretty young so he made me cry a couple of times..) and I know how much that hurts.. one fine day I simply got tired of that situation and I forced myself to start liking someone else, to take him out of my mind..its difficult at the beginning but trying to focus on the nice things other guys had and I liked, helped me a lot, eventually I started to forget about him, and I started liking some other guy that by coincidence was in the same class the first guy was, you wouldnt believe it, but when I started dating the new guy, the first one THEN wanted me..huh? for a long time I was thinking of him and stuff and when I finally wasnt interested about him anymore, then he started to seriously flirt with me well now it was payback time!! I sent the message that thanks but Im not interested anymore I say this could happen to you also..and if it does would you take her, after all she has made u suffer?
I say play her game, but dont believe it, and start focusing on other girls..little by little, maybe theres someone around you that is worth the try and you havent been able to see it cos youre sort of obssesed with this girl
the best of luck