As much as I really really don't like what she did to you by terminating abruptly and by letter, I'm coming to think that when your pain and anger about it has been worked through, you might think there is some good in this in that she didn't keep stringing you along in therapy if she felt she couldn't be helpful and useful and she encourages you to continue because she does see that you can feel better with the right therapy/therapist.

This in NO way excuses her for hurting you!

About filing a complaint, I would consider that myself but I don't know what I would do. I think I might 'suspend' that thought a while, and talk to the new therapist a bit about it.