Thank you for your comments. Sorry I've taken so long to acknowledge.

The point about this friendship being a reflection of former relationships is spot on. My stepfather, who she married after being widowed at 25 (with 2 young children), was a poor choice. In those days, women didn't have the confidence to speak out about unacceptable behaviour, so "put up with it". She's freely admitted on many occasions to not learning from it. I'm not suggesting this new friend was abusive in a physical sense.

I do think she formed this relationship because of loneliness. He was the only topic of conversation with family and neighbours (who she believed to be friends, not the gossips they've turned out to be!). One thing she was adamant about , even before he passed away, was that she never slept with him. This comment emanated from personal information his son had shared about his father's past relationships. On occasions I was genuinely concerned for her welfare, especially when they went out for dinner. He insisted on driving, although drinking. When it became obvious he had a problem, she then refused to go anywhere with him.

Then there's the effect it's had on my relationship with other members of the family. The mistake I've made is not putting my point of view. They've all believed what my mother's said about my attitude. Summed up recently by my brother's reaction when I said I'll tell you one of these days. His response, "thanks but no thanks!"