Very sorry to hear of your sadness and uncomfortable position. As to why people do these things to people they once considered friends, who knows. Self preservation is strong instint, and I think that comes into play more often than not. Also, the need to feel desirable once again after being cheated on. So they turn on the charm to the most available person, their friend's spouse.
As you can tell, I have given this thought. My H cheated with his XBF's wife 8 years ago. I considered her a friend of mine. Makes for ugly.
Be there for your daughters, but take care of yourself, as well. A year from now seems like a very long time, but a year from now this will be a drop in the bucket. Life changes constantly, that we know. Your daughters are old enough to make their own decisions about their Dad's R with new wife. My advice, stay out of it as much as humanly possible.
Go out today and do something nice for yourself. ((HUGS))
