Here we go again.

As some of you know my eldest son and family have gone non contact. He originally stopped speaking to the whole family, but about a month in he started speaking to his younger brother and they have been visiting each other.
I have no problem with this, but just lately my son has become distant towards me has said a few nasty things to me, his wife who I thought I had a good relationship with blatantly ignores me even when I try to talk to her.
It sort of came to a head for me tonight, we went to my daughters for a New Year’s Eve party, my son and his wife and there child were already there, I said hello to her she ignored me never said a word to me had a face like there was a bad smell in the room, until other guest arrived and then she was laughing and chatting with these people.
The only time she spoke to me all evening was to make sure I could still have the child this week while she was at work.
Would you ask what was wrong or would you just leave it and hope it blows over.
The way I feel at the moment is I am ok to save her childminder fees but not ok to talk too.