After my boyfriend and I broke up, his best friend told me he was in love with me and had been for a while. He has an on and off girlfriend, that is the only girlfriend he has ever had. He had always refused to let her go, even if someone else he was interested in liked him as well. It was always holding him back. One day he just confessed all of his feelings toward me and said to me "If I could make things right, I would make you mine". I didn't really know how to react, and I still don't to be honest.
I just know if he would have went about everything differently, maybe it would have made a difference. When he was there for me the most, is when I felt closest to him. I would just be there for her. Tell her that you're there and then act on it. Offer to take her to lunch or bring it by her work. It's all the little things that matter. Even if the two of you don't end up together, it's going to mean the world to her having someone there that cares.

Hope that helps.