Any suggestions on what to do? Please Help!!!!!!!!?

I've known this girl for 2 and half years and we both use to talk a lot to each other. This year (9th grade) she has suddenly stopped talking to me. I have on cl with her, but she sits on the other side of the room and she stares at me a few times everyday, but doesn't even bother to say the "hi" or anything to me. I've told her 2 years ago that I liked her and asked her out, but she said she was too young to date. Also, I have heartache just thinking why is she acting like this toward me. I feel like in my mind, I shouldn't be friends with her because she doesn't seem interested in talking to me and it has been like 2 months that she has even said a word to me. I've actually cried about this situation my mind because I don't feel like she even cares about me as a friend. What should I do? Also, why is she acting this way? Should I break my friendship with her? Please Help!!!! Thanks to people who reply to this question.