I'd let AllenA, OIN, and GMAN speak first. I would say no less than 3 months of evidence. Also confronting her is not effective, it is much more effective to burst the affair first. Then you can talk to her.
Each of these men bursted the affair, and the wife was broken out of her fantasy. They are now more effective communicating with their spouses and in various stages of repair.
Talking to a WAS ( Wayward spouse ) is like talking to an alien. They will lie even when confronted with all the evidence.
Bursting the affair is easier.
Your going to take your information to the OM's wife or GF if he has one, sit down calmly and explain the situation. Or if it is a workplace romance to present the same information to HR and the OM's boss. This is one of many ways to break it open.
