Ugh, you gotta be kidding me? There's only one answer that will work...forget it ever happened. Don't tell your wife because she 1.) might not believe your story, and 2.) might ruin a completely good friendship. Either way you lose! The way women think is as unpredictable as the weather, you cannot take any chances. If you want to screw your wife's friend then the problem is YOU because happily marrieds don't "play with fire". One good orgasm ain't worth it buddy! So many guys fall prey to infidelity that it's at epidemic preportions. Look at all you have to lose...for what? One good lay??!! Go take a cold shower and FORGET IT EVER HAPPENED.