Do I understand that you think the wife should confront the FRIEND and<quoted text>
You must be male.
It is never good to let something like this fester. So what if the girl says EWW Yuck! She needs a heads up if she isn't aware and she needs woke up if she is aware. She's a FRIEND of the neice and most likely won't be at the holiday table. In fact If she's carrying on with a married man in the family she SHOULD NOT be at the family table.
accuse her of carrying on with a married man over some Facebook chatting?
I am sorry, just don't think that alone would be enough. Now if that chatting was sexual, or the wife finds cell phone calls or texts to the FRIEND, then I think you have a case.
Let me explain the Thanksgiving reference..wife confronts FRIEND with little evidence, FRIEND tells niece that her Aunt thinks her Uncle is a perve and/or a cheat..niece tells rest of the family..Uncle could be wrongly accused. Never meant to imply the FRIEND would be at Thanksgiving.