I can see there is a lot of games like this, and i've been playing some random ones without luck. Is not that easy to find a good one. The only good one i've played so far was "Good girl gonne bad".
In Nymphomania Paradox you can start dating your childhood friend, and then immediately cheat on him. I'm not sure if this fits your criteria because it's not focusing on the "cheating" and more "the woman being/turning into a massive slut".