I'm going to swim against the current a little bit here...
From what I am reading the affair has been over for probably more than a year? And you have no reason to think that it's continuing. If that's the case, and she is willing to be completely transparent about the contact she still has with him, I might be able to live with a slight exception to the absolutely no contact policy. There are a few parts to my thinking. Part of it is that you keep your friends close, and your enemies closer. This way you know where he is, and what his connection with her is. So, that's part one. Part two is that at this point I think it's too late to try to enforce the no contact policy. That horse is well out of the barn. To try to do it now is going to look controlling, and she is also going to think that you are trying to punish her.
I understand your anger and bitterness. If you want things to work, you need to work on the healing side of things now. You know, in your case, a Retrouvaille weekend might be really helpful. I think the two of you could use a good chance to reconnect, and get to understand each others' feelings.
