I agree that eventually it needs to end but I don't think now is the time to push for it.
Everyone I have talked to that knows her well says I should just back off right now and wait a bit. Even her best friend who thinks she is [censored] up majorly told me to just wait this one out for a little bit. Not indefinitely but at least a few more weeks.
Wait for the affair to die down?
Really?
You're taking advice from her friend?
Is she closer to you or your wife?
How do you know she didn't agree with your wife on having an affair with another man?
If your wife is having an affair, your actions should be quick and decisive.
Waiting and allowing this crap to continue is just that, waiting for crap to continue. There is no benefit to this.