Do you think you could do that? Say nothing! I can't imagine you could do that. She would prob. keep lying about the OM, and saying how she has no intention of dating and you would just sit there and listen to that?
And I think if you say something and don't have any consequences, she will lose the remaining respect she has for you, and you will lose some of your own self respect. At least that happened in my case.
I think when WAS are having an A that DBing doesn't work. Well it works for you, but not on the WAS. It doesn't work until when/if the affair is over or on the rocks. Which I 100% believe will ultimately happen. Anyone that gets involved with a married woman has got to be messed-up in some way.