(((Almedafan)))
I don't understand why your mother has anything to do with your therapy. My mother is not alive but if she was she wouldn't know what was going on, I can guarantee that. I don't discuss my therapy with anyone in my family, except sometimes my husband but that's only sometimes and some topics.
I think that if you are worried about T ending your therapy, then you should discuss this with him at your next session. Maybe he was just trying to help you manage your mother and get her off your case. Ask him why he wants her in your session if you don't want here there!!
It's time to cut Mom loose on this one and take care of you. You deserve it.