WIBTA if I continue low contact with my mom.

I (40m) and my mother (83f) have add a rocky relationship for a while now. It started after the world opened up from the pandemic when I asked her if she wanted to meet my then girlfriend and she refused. The reason she refused is heartbreaking to me and I'm embarrassed to admit it but my mother did not approve of my then GF because she was black. I went low contact then. After that relationship ended I suppose I started talking to my parents more but it was never the same as it was before.

Fast forward to now I am happily engaged to my fiance (38f). We have been together for a little over a year and my mom couldn't be more disappointed. Shortly after meeting my fiance, at the time my gf, she sent me a very long text message telling me I needed to slow down and that I needed to be careful that she might be after my money. I come from a wealthy family. I do understand that it looked like we were moving fast since I did not tell her about this relationship for the first 8 months and they didn't meet until around a year. I guess there was still a sour taste in my mouth from last time I tried to share a relationship with my mom. My mom continues to show me that she does not approve of my fiance and told me that I was settling when I told her I had proposed. I decided to go back to low contact I pretty much just send my mom pictures of my son (8) and updated on him. Last week my son's mother, told me that my mom had told her she was depressed. I took offense to this as it has become apparent that my mom and my son's mom have now developed a friendship behind my back. Just for some context my son's mom was abusive to me when were living together, she constantly accused me cheating and did what she could to isolate me from my friends and family. She had also said some of the most hurtful things to me I've ever heard, biggest example telling me I was put for adoption because my bio mom knew I was a mistake. I'm adopted too sorry my life seems to be as complicated as a soap opera. This friendship between my mom, the person who raised me, and my son's mom, the person who made me feel the lowest ever have in my entire life felt like a betrayal. I called my mom to tell her that I felt this way. This conversation did not go well. She took up for my son's mom and said that my fiance was treading on my SM's territory by calling my son her "bonus son". My son's mom and I have always thrown my son joint birthday parties but this year my son's mom would not show up because my SO was present at the party. My mom tried to blame me and my fiance for this. I told her that it was her choice not to show up. My mom moved on to why weren't my son's mom's parents invited. I just said that they weren't my responsibility. I will invite them should there be an issue next year but I still don't feel that is my responsibility but tell me if I'm wrong. My mom said that my fiance was trying to isolate me from friends and family and I gave her multiple examples of how my fiance is very supportive and plans game nights and parties for me to get to spend time with friends. I also provided examples about how abusive my ex was that isolated me. My mom said "yeah that's right but I just don't think you are good together". I told my mom she needs to get to know her and that my fiance wants to get to know her and my mom replied "if she wants a relationship with me then I'll ask her why she dyes her hair weird colors they make her look like a clown". I pointed out name calling is rude and she said that she never called her a name and that I was twisting her words. Our argument ended with my mom telling me she tired of talking to me and that I needed therapy. When I reminded her that if been in therapy for 10 years her response was "it doesn't seem to be working" So would I be the assconaut for going low contact with my mom?