I've cheated before, it's not fun at all. You get some worked up with emotion and when you are with the person you shouldn't be with things get out of hand. I feel so bad for the girl I cheated on, I went and told her right away. I felt like shit, Yay for 5 seconds of pleasure and a lifetime of pain. Don't urge her to breakup with her current relationship, but if she isn't satisfied then thats your chance to strike.