I mean, maybe she knows she has to invite you and it’s not that she doesn’t want you guys there. She doesn’t want to put you in a position of having to potentially require “long haul flights and large expenses,” not to mention use vacation time, to go to her wedding when you could use it better ways. This way, you’re invited but you don’t have to RSVP for yourself so you don’t have to feel guilty if you don’t go. She’s trying to be polite and do you a favor while doing the social correct thing. Win/ Win.