Hmm, if it was me I think the only thing that would keep me from going crazy would be to remind myself that she would be the one that everyone was talking about behind her back once they left, not me. At least that's how it works in my family, if you act like a spoiled brat, everyone will talk about you as soon as they can. But maybe you could suggest to her that if she's not coming to the reception it hardly seems worth her time to drive 5 hours for a twenty minute or less (unless you're having a catholic mass) ceremony. It might be worth a shot.