Sorry D, I was wordy and confusing, making my story about me instead of you.

I don't think you need to have a friend talk to your T. I was trying to say that I think you can have your mother talk to your T in a way that maintains boundaries, safety of the relationship and clarity in your mind about who T's alliance is with.

Don't give your T or mother each other's contact info. Instead, initiate contact yourself with your T's support/presence - for example, by calling her on speakerphone during a session, or by crafting an email or snail mail letter together and then reviewing the response in session. If you are present for any interactions between your mother and T, you can discuss those interactions with T afterward and worry less about manipulative garbage.