I have had an experience where I had to make that choice. My ex-husband kept lieing to me about her. And he was lieing to her about me. So when he was gone on a business trip I decided to invite her over to take me grocery shopping. We talked on the porch for about an hour and she had no idea he was sleeping with both of us! I showed her text messages that he sent me and told her that if he ever slept with me again I would tell her. Which was a really bad idea. I kept sleeping with MY HUSBAND and would text her immediately afterwards just to piss both of them off! This woman was so lonely and vulnerable she continued sleeping with him! She left her husband for mine and he left me and his four children for her! Now they are married and he doesn't work, or go to school and we got divorced! They have 6 kids together and they see um every weekend. In the end it all worked out, but because of the games I played with both of them, and the fact that they FAILED miserably, made me absolutely hate them. I'm a pretty kind person so this is horrible! To have all of this hate in my life is a chore! I've tried to get rid of it and forgive him and it's been almost 3 years now and I can't! Yes, once again, i got tested for STD's and i'm clean. So take my advice, only confront this mistress if you think your spouse is lieing about things, you can keep a cool head, and you know for sure you can fight the urge to play games and use them against each other for your own personal satisfaction in knowing your hurting them as much as they hurt you. Sure, it's a great idea in your head when your all hurt and confused, but when it comes down to it, it just makes you the loser.