She'll probably hate you the rest of her life.
This. Seriously, life isn't like a RomCom, and the other guy is probably just as good if not better than you. What's the old law? If you think someone is attracted to you, you're wrong. Also, she agreed to marry him, she's had a long time to think it through, she's not just going to abandon that over you bursting in there.
Everything you stand to achieve could be received eventually elsewhere, and you stand to lose so much (Her friendship, her friend's friendships, the grooms ability to see you without flying into a homicidal rage)
Life != Romantic Film.
!@#$% what Hollywood tries to force down our necks about it's concepts of love.
!@#$% Hollywood.
!@#$% them all.