Why does she suddenly ignore me?

About 3 years ago I met a girl on the corridor at work. We just exchanged glances. We kept seeing each-other at random moments on the same corridor and simply exchanged hellos. Then she suddenly disappeared. A few months ago she joined our department. Apparently the project she was involved in failed and she among other people was fired. From that moment, as days ped by, we grew fond of each-other. But from our long talks, there was always something missing. We never talked about us, or share our feelings directly. Instead, there were all these small little gestures that suggested me we had a good thing going on. I learned from a friend of her's that about an year ago she ended a relationship with a guy just before marriage, so I figured she hasn't fully recovered and was in a delicate emotional state. I was patient, letting things flow in a natural way. Then about a month ago she simply stopped talking to me. I try to talk to her, but she either smiles or just changes the subject, mainly to a work related one. I looked back many times, hoping to find the reason. I feel ackward and blame myself, but for what, I don't know yet. I'm out of ideas and I don't want to give up, because I care too much for her.