confused buddhu

Hello my dear friends, I am a very sensitive kind of guy, who rarely makes friends. Once i met a girl, as the time was passing by, she became soo close to me, she’ll spend hours with me even if she barely gets time to study(we both were good in academics). One fine day she proposed me, and even i gave her a positive reply. But after few months, she suddenly said that she doesn’t want to talk to me. What could be the possible reasons for that? Even now shez my classmate, but still she never speaks with me, and she is not in an relationship with any other guy too….