I'd confront the guy and beat his azz in front of all the homies while we're at the bachelor party, throw him through a door and threaten to throw him off a balcony while a pimp and a couple skrippers below watches on.
Another homie will probably talk me from tossing dude off the balcony, then I'd call the wedding off.
The next day, I'd show up to the church to tell my parents the wedding was off, but then the guy that she cheated with would show up, we'd pray on it, then I'd reluctantly get married anyway and cry at the altar like a bytch.