I have basically the same issue. It's gotten better though because I haven't seen her in almost two weeks. I was seeing her for probably like 3 hours a day five days a week for 9 weeks. Not all of it was individual I should add. But even still, that is a LOT of contact and boundaries were blurred.

T and I set very strict rules on outside contact. It is for emergencies or scheduling only. However, if T is worrying too much about me being in my abusive parents house and wants a quick update, she may just shoot me a "are you still breathing" email. She never responds to me when I email her unless she wants to just say a line of general support.

T said she doesn't actually believe that me feeling like she is my mom is bad. She thinks I need to experience being mothered and that's why she plays the role with me. She also is naturally maternal to me. The problem arises when I start asking for more than she can give. She says no mother can fill the shoes I want her to and when she lays down that boundary, I feel rejected.

So I'm not the best person to answer this, but do you think you could try discussing with her having no outside contact unless it is a crisis? That might help.

Also, T is a part of your life. Just because I can't be a part of my T's personal life doesn't mean she isn't part of mine. I know a lot of you will passionately disagree with this, but if I am actively working on accepting/learning how to keep healthy boundaries with people, what is so wrong with me literally thinking my T is my mother? "Because she isn't actually your mother". So? My biological mother didn't even start to fill the role. How am I supposed to know what the role even looks like? T does fill parts of it. I want to tell her when I do things right, she comforts me when I'm sad, she helps me take care of myself. I just need to work on accepting that no one, not even if my biological mother completely changed, can totally play the role I want her to. No one can actually be there 24/7 whenever I need her.