I'm so sorry it came down to this for you, in the end. I know you've been agonising about it for a while now, and it's going to take time to recover from something like that.

I agree with some of what the others are saying - this could continue to bother you unless you deal with these feelings somehow, and the best way to do that might be to have a final session with your therapist. Otherwise, do seek out a new one to help you deal with your current sense of loss. I understand that the grief you feel is overwhelming at the moment, but I feel it is important for you to not go through this alone.

I'm currently having some of the same feelings about my academic mentor. She's a trained psychotherapist and she has helped me so much, but I've become overly attached to her, which honestly terrifies me. This woman has even told me that she thinks we have a "special relationship" and that she's so glad she gets to work with me, etc., but then the other day when I told her that I'm worried they won't offer me mentoring next year, she sort of casually said, "Well, if you ask for it, I'm sure they'll give it to you." It was said in a way that made it sound like either way, it made no difference to her. It is rather painful to be confronted by the reality of such a relationship.