My son is in his midtwenties, and is engaged to and living with his DF. They've been together for about 8 years, and I think she was his first GF, certainly the only one he has ever mentioned or introduced. I have always found it difficult to like her or even get to know her; in all of that time I have only heard her chat freely once, and was astounded at her cattiness and lack of empathy, but I suppose she's young. (I made no comment at the time, nor have I since.) They are due to marry later this year.
She has a difficult family background and this has caused her problems with insecurity and self-esteem, including eating disorders; this was disclosed to me when every invitation to a family event resulted in her being "sick" at the last minute. Despite not having a "chatty" relationship, she has confided in me about some events in her past and ended up sobbing in my arms a couple of times. I have suggested counselling, offering to drive her to appointments, and even sourcing the help available, but she has taken no action so far as I know. I concluded she's a bit of a drama queen (understandably) and left it.
Until they moved out about 15 months ago, they both slept in my home 3 or 4 nights a week, spending the other nights in her home. They would come back from work or college, collect their meals from the kitchen and vanish upstairs to eat and watch TV in his room. They did not participate in family life at all, did no housework and paid no rent, but DH and I left them to it. We were, tbh, relieved when they moved out, as DS had constant clashes (verbal!) with his dad and younger brother and the atmosphere could be uncomfortable at times.
So far, so normal.
However, since then she has decided that she hates me, and is refusing to speak to me. Xmas gifts were pointedly from him, not them. When I asked DS what was going on, he told me his DF feels I betrayed her confidence when I spoke to a friend when seeking help in supporting her with her eating disorder; said friend is a bit of an expert on the topic and the information I disclosed to her has gone no further. So yes, I did breach her confidence but only because I was worried about her, and I have apologised and explained this to her, but my apologies are not accepted. DH is included in the "not speaking to" category by virtue of being DH, and DS2 is also included because of the sibling rivalry going on when they all lived here.
DS feels caught in the middle, but is still speaking to us and even managing to be civil to his DB now they live apart. He's in a difficult situation and none of us wants to make that any worse.
However, DH and I recently bumped into one of DS's good pals from school, and were disturbed to realise that DS hasn't seen him in over a year. Plans had been made a few times, but cancelled at the last minute when DF was "sick." DS2 met another of DS's old friends (DS was best man at his wedding 18 months ago, this couple introduced DS to his DF) and he hasn't seen DS in a long time either. The married couple have often invited DS and DF to social events, but every time DF was "sick" at the last minute. They haven't even seen DS and DF's new home.
There are other examples, he has left one club, drastically reduced his involvement with another, and given up a third pastime he had recently taken up, all since moving in with her. They live in a property belonging to her family, in her village.
So, if my son were my daughter, I'd be sitting her down for a chat about red flags and abusive behaviour. I'd be pointing out that DF is attempting (and achieving) to isolate her from friends and family, and is emotionally manipulative. I'd maybe even say that, damaging as DF's background was, it doesn't excuse such controlling behaviour in the here and now. I might point out that DF cannot be "fixed" by love or responsibility alone.
But I have a horrible feeling that attempting such a conversation would result in a complete break from family. What, if anything, can or should I do? Keep my nose out and not be an "interfering MIL from Hell"? Or attempt the talk and maybe make everything so much worse?