I think your reaction is natural for someone who has had a person in your life for 12 years and now may lose them. Go easy on yourself, your feelings are all valid in this. Even feeling like you have to distance, it seems like a protective method and many people do it. It's ok not to want to continue therapy with her. I say meet a few times maybe? Send a card and make peace with her.

My therapist is not at all the person i googled, her life has changed so much. I wouldn;t normally go and see the person i thought she was but I gave it a shot. Turns out that was the right plan because she is so much more awesome than I thought.