Guess I would start by finding out what is causing her bitterness in the first place.

I am coming from a many year marriage (33). My husband from the beginning was very irresponsible even though he was the nicest person & would do anything & everything for me as long as he didn't have to be financially responsible or have to cooperate with what I needed. I wasn't wanting to get married from the beginning after I realized what a immature jerk he really was, but "the invitations had been sent out". My Mom assured me that he would mature & become responsible as he got older. Well, he never did. I stupidly allow him to run our finances into the ground by his use of credit for everything (even though I knew in my mind it was wrong). I bailed us out once & showed him what he needed to do. But when I ended up with anxiety & major depression after loosing my career, he could not conceive that I couldn't be going back to work. He always stuck his head in the sand every time he needed to be responsible & he continued doing that even when it was very important for him to take over the responsibility.....he drove us so far into debt & he had no idea how to live in the world of reality.....there was nothing that could keep me from the horrible angry feelings that I felt toward him.

Those bitter feelings usually don't just happen for no reason unless she has been abused by someone else before getting into the relationship with you. If it's something you did that caused her bitterness in the first place, it's very difficult to build back any trust that would be needed to get rid of the bitterness & giving her love has nothing to do with how she is feeling.

However, if her bitterness is coming from something that has nothing to do with you (say she was abused by a previous BF & is taking it out on you).....then I would suggest therapy for her & possibly couples therapy for the both if you are expecting this to go into a serious relationship.

It would be in your best interest to find out exactly where the bitterness is coming from so that you could determine if there is actually something in her past that caused it or if there is something you are doing in the relationship that yu need to change in yourself even if you can't recover this relationship, but maybe it could help your future possibilities in relationships.

I would suggest determine where the bitterness is coming from before taking any actions at all.