You need to drop the bomb—or, rather, place it down gently—like, today. Then it's her call. If she opts not to go ahead with the trip—or to go on her own or (sorry, dude) with someone else—you'll have to suck it up, since (a) she's the one invited to the wedding, and (b) you're the one doing the dumping. Best-case scenario, she'll agree to go with you as friends. And if her next boyfriend happens to be seated on her other side at the wedding, she can tear up the dance floor with him while you daydream about your new girlfriend back home.
Cathi and Dan give advice on whether to break up before or after a trip.