Is it possible to be totally supportive of someone and to also be abusive?

I have been dating this woman off and on. She is my best friend and I support her dreams and hopes. I tell her she is the most beautiful and amazing woman on the world. I tell her she can do anything. When she is down, I try hard to build her back up. I write her cards , letters expressing these feelings. I like to buy her things "just because". But also sometimes when we are misfiring and I can't seem to understand her feelings, I get frustrated and after a while say things like F' off. I hate myself for doing those things because I really want her to feel how amazing she is. I have lashed out like that maybe 6 times. Once or twice in public. 1 time it escalating to the point of me throwing an umbrella. I go to a therapist and he says that the amount of good things I have done outweigh the bad and from time to time relationships go through turmoil. He says that while that is abusive behaviors , that I myself are not abusive. I'm not so sure. The woman in question while she says she loves me, no longer trusts me and the relationship has ended. I do not exhibit controlling behaviors or have I ever called her a name, or insulted her. But I am aware that she doesn't speak to me that way and that telling someone to F' off is wrong and degrading. I would love to gain her trust again but not sure if its possible.We have been hanging out for 2 months and it has been great.I know I have to be more in tune with her feelings and be willing to make sacrifices for her needs and I believe that she is seeing that. I really feel that we connect and that she sees how much I truly love her.She has gone and said that nobody knows her as well as I do and told people that we were talking again. Last week she just told me I had to let her go. I know she is conflicted and I also know her parents and best friend do not like me. So i sit in wait in limbo and try to give her the time she needs. Is it possible to regain her trust? Any insight would be appreciated.