I'm sorry you have to go through all of this; it's definitely not fair to you.

This may be a silly question, but have you told your T how upset you get when you and her talk about your mother? You shouldn't have to feel hurt by your therapist when you leave your session, so I'm not quite sure your T understands how much it hurts.

I think you literally have to state your feelings about you and her having discussions about your mother, and say that you want to work through these feelings so that you're not upset every time you leave therapy.

Good luck