Okay, I'm stepping in late, but I have to give you my comments because I consider myself to be a male's advocate. It's a necessary role to play because women have lost all sense of decency and responsibility in this country.

I know this hurts/fuckings sucks, but consider yourself lucky. You found out the truth about women. No, not all women are like this - but MANY are. You now have the upper hand. Use that to your advantage.

First thing first, get your head on straight as much as you can - find your own emotional stability right now. Do not go into anything with an emotional state - women are masters at emotional manipulation - if you show weakness here, you are fucked. If you tell her what you did, you are also fucked. The typical woman will take what you did and use it against you. The blame for everything she can think of will be placed at your feet, she will not take responsibility for anything (in fact, she'll twist the whole conversation so that it's not even about her misdeeds, it's what YOU did wrong as a man) and after this conversation of insanity, she will feel like she is justified and guiltless. And you will think afterwards 'wait, what the hell happened, she IS THE CHEATER."

To echo my man's thoughts here:

Originally posted by noboost
I honestly wouldn't do anything with the evidence or even admit you've seen it. She's going to use that as a platform to make it your fault,

DO NOT ADMIT THAT YOU SPIED

Next, make the choice that you are prepared to live with for the rest of your life. Do you want to fuck her over? Or do you just want to shut the door and move on. The choice is yours.

If you decide to mess her up, your choices are almost endless. But make it completely unexpected, make it big enough that it has an impact on her, and make sure you come out of it with more dignity in her eyes than she's probably ever had for you. It will teach her something too.