In this case I think I'd tell her of all the ways she failed. I know that sounds bad, but maybe the feedback would help someone else in the future. If she helped you in any way you could mention that too. I wouldn't take a gift or letter. I don't know.

The first therapist abandoned me so there was no termination session. The second was moving away and we had a great last session. I gave him a letter and he gave me one. But with a "bad" therapy relationship I don't know. I haven't been through that kind of session.