Sometimes I don't even know what to do

I could really use some advice. Rarely do I have a problem with shit friends. I'm pretty selective with my friendships, if acquaintances don't become friends I drop them. As a result I'm close with my friends, value them and try to go the extra mile. It pisses me off when I don't get the same. I spent two months of summer hanging out with a girl I'll call Y every week. (More frequently then I see some older friends) I brought her to my club on Toronto Island, taught her how to cook stuff and we hung out with her friends and generally had fun. After she visited her bf in Cali for a week I haven't heard from her since aside for a quick phone call and a couple of fbook messages, just saying she was busy. So yeah its kind of the cranky bit of my general excitement about school, hot TAs, clubs, newspaper articles to write etc. I would let it go I think... but she has my favourite bronzer and its like the insult to injury. How would you solve this?