Still letting everything sit in my head here as I ponder it, there are lots of good comments in this thread; but as far as my part goes, I just realized that I very much trust my intuition / sense of people to tell me what their intentions are (I think I can detect inconsistency and duplicity in their response). Because of this, I don't really need the external signs as a sign of proof -- I don't need to control or demand anything -- if i sense the heart is right and wants to make amends. So that frees me up to be more flexible in my forgiveness.
I also can think of a few times where I would refuse to accept an apology because I knew the person either didn't mean it or would not commit to actually following through on their good intentions, and that was intolerable; or where I turned away a gift because I felt like I was being placated or "bought out" rather than the person giving me something out of remorse and with intent to improve.
I remember complaining about my roommate a few weeks ago, because I was feeling that way -- many many slights, let-downs, disappointments, etc., where she did not live up to her side of the friendship, and stupid little signals (like hugging me and saying she loved me, or buying me a meal) did nothing to improve my bad feelings because I felt as if I were being purchased without any intent to change or true exploration of the problems. When she finally did have the courage to ask me why I was upset and face my potential anger, and she apologized on her own for some of the things without making excuses or justifying her failures, then I felt better.... as if she finally realized what she had done and why I was so hurt, and I do know that she doesn't meant to hurt me.
However, like I think Fia said, while I have forgiven her for those things she showed awareness of and apologized for, I still can't make myself as vulnerable because -- while her intentions are good -- I believe she still isn't quite trustworthy due to her willingness to sacrifice what I need for what she wants, at times. When she wants something for herself, she just can't bring herself to say "no" even if it is at someone else's expense. I just sense her heart is still focused on herself in some ways.