You say "I told you there would be no further discussion
about this issue. What else is new? Have you heard from sister? Is she enjoying her honeymoon?".
If they continue to press the issue, you say "Since you seem to want to discuss a subject that I consider closed, I'm going to go now, as I have to tend to hubby who still isn't feeling well from his chemotherapy for his incurable cancer, and thanks for asking, by the way. I'll talk to you soon".
And then you hang up.
And then the next time you call, you act like nothing has happened, like their totally unrealistic attitude hasn't fazed you at all.
I have a SIL like your mom. Her goal is to get people riled up. The best way to tick her off is to be indifferent. People like your mom and my SIL control us normal people because we inherently think that their bad behavior is going to change, so we expect them to act like we would in various situations and they are mentally incapable of acting like a normal person. I will repeat that line again....
they are mentally incapable of acting like a normal person. They are only capable of acting how they act, which is not normal. Once I came to an understanding and, yes, acceptance of that, it made dealing with my SIL a lot easier.
How I deal with her is quite simple...I make my decision about a particular topic or issue involving her, I state my decision, I do what you did, and tell her that it is not a topic up for any more discussion, she has heard my decision, she will not change my mind. And then I do not discuss it again. If she brings it up, I say "That is not a topic up for discussion. Goodbye" and I hang up the phone. I do not argue, I do not explain. I decide, state, and end the discussion.
It has made her infinitely easier for me to deal with her, since she knows my decision is my decision.
And yes, people have told me it is controlling on my part, and it is. I am controlling the amount of stress and aggravation she brings to my life. There is a long history of why I came to the conclusion that this is the way she needs to be treated, she is the only person I treat in this manner...anyone else I am more than willing to discuss, explain, listen, compromise etc. Not SIL though. And frankly, she adds nothing to my life, so if one time she got angry enough to cut off all communication with me, it wouldn't faze me a bit, and would actually probably be a blrssing.