My MIL is a manipulative, destructive person with undiagnosed mental problems. She has made life very difficult for her two sons and successfully estranged the boys from their father for more than ten years (they are now in touch). She also gave me hell when I started going out with her son. Called me a predatory female and offered me money to go away and so on.
The sons have always been very close to her and she has excercised her power over them even as grown-ups. My husband did break away from her to some extent a few years ago and while he has had a cordial relationship with her since then the emotional bond between them has not been the same.
Today I accidentally saw an email from my husband to his mother referring to her as "Dear Mummy". I found that very weird and upsetting given the history and the fact that in my opinion grown-ups don't call their mothers "mummy". My husband says this is common in Britain (I'm not British). AIBU?