My Mother used to go through all my drawers, and under my kitchen sink and then declare it was filthy. My Dad still gets my mail for me which is a Federal Offense. I discussed it with my therapist many times. Finally she said I needed to lay down a hard and fast law with both of them. If I see my Mother coming close to opening a drawer I tell her "get away from that" " Do I go through your personal things?". Then she stops in her tracks. Setting firm boundaries are the best things to do. And you can sound like a Parrot and repeat the same thing over to her. "Mom I don't like it when you do this". " If you continue to do that I can't have you in my home or maybe in my life". Some Mothers are very controlling and over protective because we have a mental illness they feel they have a right to be into our personal lives.
My mother was very cruel to me when I was young, but she treated my son very good. I used to joke she was not the same woman who raised me. Then when he was about 8, I dropped my son off for her to watch overnight. When I called him in the morning, he started to cry when he heard my voice. I told him to go in the bedroom and wait for me. I’d be there in 15 minutes. I walked in the house and calmly told her she may have treated me like crap, but if she ever treated my son badly again, she would never see either one of us again, and we left. She didn’t drive and she had my dad drive her to my house. She apologized and said she would never do it again. She kept her word. And we enjoyed three good years with her until she died.