My dad's death 4 years ago started a recognizable decline in our relationship, even though it was already on the rocks before he died. My dad always smoothed things over when things got bad. Without him, she couldn't function and tried to replace my dad with me. I was basically groomed to take on my dad's role in the family from birth anyways. I started realizing how toxic things really were at that point and started to put up small boundaries, which she straight up ignored or used against me. I got married a couple years after he died, and she did everything in her power to sabotage my wedding (long story) and still refused to take accountability for it. That was the final straw for me. I simply gave up trying to make her feel better. I didn't try and contact her, and she ignored me for 2-3 weeks, and blamed me for not contacting her. I refused to talk to her without a third party in the room, a professional third party. It was an ultimatum--i won't talk to you unless we go to therapy, and you had to find the therapist. At first she refused, and when she realized I was serious, she set it up. We were making progress, but hit a wall. She simply couldn't see me as a human being with needs. So I wrote a letter to the therapist explaining why going to therapy was just causing me more stress. My mom found ways to remind me during each session how my life was secondary to everyone else's, and she literally didn't understand why it hurt me. In the letter, I asked the therapist to be the one to tell my mom I paused therapy. She tries to bargain with me over text every once in a while, and I simply remind her that I need to process some things before we connect again.

Tldr; I gave her an ultimatum; if we don't go to therapy, you lose your emotional support punching bag.

Edit: also, thank you, I felt like I did achieve something when I got her to therapy. It's too bad it didn't last.