Do you think about her alot? Do you think that it is possible to get an honest answer from her if you were to ask her the question "Do you think of me alot?". You write about her with feeling, I can't help to think that you really do love this girl. I was like that over someone, having trouble still letting go. Sounds like she may still be into you but there is no way I can tell either. Do you know any detail about how close she is with her boyfriend...and I don't mean sexually...just what does she think of him and how deep her feelings go for him?
Do you know what I would do? If I trusted the girl I would tell her the problem the same way you told us. I don't know exactly though what your situation is though, only what you tell me. If you tell her that you are having trouble letting go and are undecisive about the entire situation because you fear losing her then she may tell you how exactly she feels. You did say though she kind of got teary eyes when you spoke of this with her. Unfortunatly this means you have to actually be a bit emotional with her and let her know what you think and hope she takes it with maturity. I don't blame either of you for dating other people, that is not what I meant, I just thought she might have moved on....but it seems there is more to this.