My H will also tell my mom things. I am never sure if his intent is to try to get her to set me straight on things. Or if it is to find out things I might have told her,
Just this summer he discussed with her how emotionally closed off I am (lacking affection) and how terrible of a person I was for not wanting to have sex with him all the time.
My mom assured him that I have always been reserved in my emotions and that it amazes her the physical affection and openness I show towards my children because it is so out of the norm for me. She left the sex part alone I believe.
When I left my H and up to the point of me leaving her. He was calling everyone I knew and was talking to them of our problems. Why? He also told everyone he even slightly knew of our problems. Maybe he was just needing someone to talk to. Or he thought he could get them all on his side to tell me how wrong I was who knows. All he ended up doing is giving himself the lable of my psyco husband to most people and they still refer to him that way when they speak of him to me.
If your mom is concerned I would not tell her it is none of her business I would just blow the conversation of with a nothing has changed or change the subject. Enough times done she should get the point. I will usually just tell people I don't want to talk about it right now and its a done convo.