It is interesting what you wrote about your mother; where she felt like her own parents were watching over her in a disapproving way & waiting for her to fall. I wonder if way back here is when the concept of ‘all being well’ was established? It was a protection mode for her: ‘see all is well, I did not make a mistake’. Perhaps she felt she could never make a mistake? and then it became the same feeling she had with her friends, social group - if they knew, they would disapprove, she would be rejected, left with all her insecurities and failures exposed.
I sense both the frustration/anger & the compassion that you have for your mother. It most definitely sounds like you have been working a long time to heal this relationship, and also to heal the pain inflicted upon you. THANK YOU so much for sharing the analysis of your therapist; I wont quote it here as it was long, but the insight on how a child learns to not expect from the addicted parent; but puts their trust in the other, and then feels the pain much deeper when they are disappointed; that is very enlightening.
I think ‘trying to mend’ is a healthy part of understanding & acceptance, but I also think when you get no effort back like what is happening in your case; and continued interaction causes such pain, then you do need to create some distance. I feel your sadness in needing to make this choice. Your mother clearly is missing out on what could be a deep and caring relationship; hopefully one day she will see this & reach out with willingness to change.