'Relationship' help!?

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So, theres this girl at my school that I really like. She knows that and she likes me (we kissed and all at parties). But she told me that there was this other guy she had feelings for too and that she would either choose me or him. She said she chose me and told the guy that she "didn't have feelings for her anymore". We talk a lot and like each other but i've been really shy to ask her out, so....yeah.
During easter break, she went to another town with her best friends and the guy was there with some of his friends (not sure if he lives there or something...). But, i've been getting really jealous with all those pictures on facebook or her posting of them two wishing him a happy birthday on instagram.
One of her friends she went on to easter break told me a few weeks ago that I was better with her than him. But i've been too confused now as after her seeing him, I thought she gained feelings for him again. On social websites such as facebook or whatsapp, we're not talking much anymore, conversations on them are really short.
Some extra info: I haven't seen her at school yet so I haven't had the chance to talk and catch up. Also, I feel quite depressive and all.

Could anyone help me with this issue? Should I still go for her or just forget about this all? I feel very lost :x