Although you can't really "teach" an adulteress, I do think you can get little "truth darts" in every now and then, and you might have said to her "(Niece was very disappointed that you ignored her all day today. She was really looking forward to seeing you. How you choose to treat me is one thing, but I think you need to say something to her." Or some such.
When you say "exposing to OM" -- you mean CONFRONTING him? Your wife's affair partner?
Not a fan of that. Elevates him in importance, you may not be able to control your emotions, you run the risk of taking ANYTHING he says and considering it as even any SHRED of "truth," and it will only get the two of them a good laugh at your expense.
