If you really love someone but they rejected you b4 should you keep trying to win her heart?

There is this girl that I work with during the summer that i still like..... a lot. Last year I told her i liked her but she ended up dating another guy over me. She told me she liked me in the past, but since I didn't do anything about it she moved on. She went away to school last yr and we talked and facebooked all the time while she was away. She told me that the long distance is the thing that will cause us to not be together * she is gone 7 months of the yr) but it doesnt matter to me. I really do love this girl.. we are both 20. I think about her all the time, we get along great and everything and all i want to do is be with her...should i tell her how i feel again, she may have a bf but im not totally sure....what should i do. If I tell her again it will be the 3rd time i would ask her to go out with me. I just cant stop thinking about her, ive never had a gf b4, and she is the 1st girl i really liked....what should i do??? i know i kep saying it but i do love her a lot