I was right then that it was possible that this was not a revenge case. Don't take it bad, we have had people in the past making this kind of post just to try to find out if they could screw up their ex-spouses immigration. I don't like this, except if it has been a blatant fraud case, i.e. the spouse married you just to get papers and then dumped you.
I think the right thing to do is to let her take care of her case, but adultery is not an issue during naturalization, not under moral turpitude/good character. Only way I think this could be an issue is if the GC was obtained through marriage, and the marriage was in bad faith, and the adultery is perhaps proof of bad faith. However, I don't know how much of an issue this might be.