My mother found out I call my girlfriend mommy
So for full context I'm a man in my late 20's, my girlfriend is in her early 30's and my mom is in her late 50's. My girlfriend and I engage in "mommydom" where she's dominant in and outside of the bedroom. She also likes it when I call her mommy during sex and just as a term of endearment. This has nothing to do with my actual mother and I don't have any sexual desires towards her. My girlfriend and I have been together for two years and engage in a lot of BDSM activities with the "mommydom" play and I'm always submissive. It's my kink and what gets me off. I can't explain it.
Well as for how my mother found out it's really my own fault. I have my girlfriend as "Mommy" in my phone and my mom as "mom" and my girlfriend gets off when I send her pictures at work. She made me wear a chastity cage for a week (a cage over my penis to deny it any stimulation, keep it from becoming erect and it has a locking mechanism so I can't take it off) and I accidentally replied to mom instead of mommy via text message with a picture of my penis in the cage with the text message of "I'm trying to be a good boy mommy but the cage is so tight. It's coming off tomorrow right?" I sent a picture of my penis in a chastity cage to my actual mother.
Obviously she responds with "What the fuck!?" Then immediately starts laying into me via text. I explained at surface level what our relationship is and said it was "Gross" and that she was ashamed. She got into a text argument with my girlfriend as well. I talked to her and she eventually calmed down and said she reacted poorly and apologized but she just begged me not to ever hear anything about it again. My girlfriend was still angry about names she called her though. But my mom invited us to dinner. My girlfriend was wearing her coat since it was cold and during dinner my girlfriend took off her coat and she was wearing a very low cut shirt that says "Your son calls me mommy too." The moment she took it off my mom yells "Are you FUCKING KIDDING ME!?" Then they started fighting.
We ended up leaving early while my face was incredibly red during the whole drive back. I'm trying to get them to reconcile and my girlfriend agrees that was petty and apologized for her behavior but my mom is still angry with both of us now and I don't know what to do.