I can't get my mind off this girl...?

she used to be my best friend in hs and i have always been somewhat in love with her...we're 19 and in college now and some stuff happened in august of last year and i havent seen or talked to her since...in hs she used to say that after hs, when we were in school we might be together and that gave me hope...then in the summer of 2009 she started dating my ex...anyways long story short, she disappeared until august of this past year, and some things happened in this place called "the quarry"(a shopping/recreation area in san antonio, tx(where we went to hs and now both actually are in college here, two different schools...)we made out and she was telling me that she had always loved me but had never had the balls to tell me like i always told her how i felt about her...and then i saw her once more a couple days later, but the feeling was different, like her aura, and i knew something was wrong...she said to wait for her at the public library by her school because her mom was coming to get her last minute and her mom dislikes me...i figured since i had no car and had already taken 3 buses to get there that id walk to the library and wait...i waited for hours for a call that never came...i never saw her again...i just dont know how to get her off my mind...i have a gf but i still cant help thinking about Bre(the girl)...i wish she was still in my life but i cant contact her because she blocked me from facebook...i dont even know what went wrong...ive tried contacting her asking if she would just tell me what happened to no avail...what can i do?i want her to be in my life, but if she wont how can i stop loving her?