Bisexuality Support Group
Bisexuality is a sexual orientation which refers to the aesthetic, romantic, and/or sexual attraction of individuals to other individuals of both their own and the opposite gender or sex. Most bisexuals are not equally attracted to men and women, and may even shift between states of finding either sex exclusively attractive over the course of time.
Maybe she was scared of being bi/ gay back then. Maybe she loved you and couldn't tell you, for whatever reason. Years can change people, and maybe now she's trying to be her authentic self :)
Straight guy was going through a really bad time, and turned to drugs and alcohol to deal with it. He was in several bad relationship with girls. Our gay friend stuck right there with him for a long time trying to fix him, with no luck. So gay friend told him they could not be friends anymore.
A few years later straight guy finds gay friend, and told him that he was the only person that had ever really cared about him, and he wanted to straighten up his life and asked for help. He also had decided that since gay friend loved him the way he did, and had made him take responsibility for his actions, that he was willing to try to have a relationship with him as long as they took things slow.
They had a good relationship for a couple of years, then straight guy, got back into drugs and alcohol, so gay friend told him that it was over.
What I am trying to say is, that you need to think really hard about this situation, and decide if you want to give her a chance. If so go for it. Just take things slow and keep your eyes open and on her for a long time. Watch out and make sure she is not taking advantage of you. She could just be looking for someone to bail her out of a bad situation, and is exploiting your love for her. But, she could also be legitimately trying to straighten up, and knows that you are the one person that loves her enough to help her through this hard time.
I wish you the best of luck, and keep us updated on the situation. We can help you keep an objective outlook on the situation, and see things that your heart wont let you see. I hope it works out for you.