Friends? Sorry but that was kind of funny...if I was him, I'd probably hate both you and what you did, and flip you off if opportunity had presented itself.
You wanna know what a guy's mind thinks when a women cheats on him? Here:
"Why did she do it...?" -Wrong! Try again.
" *%#&¤?§* !" -Correct!
Ultimate betrayal as mentioned before...you wanna hurt him more? Try being friends with him, that should help.