So of course she changed for the afterparty into something even less memorable. And it's so HEAVY. And it's not really that much shorter, which is usually the reason to change: either you have a train that might get ruined at a post-party, or it's too intricate to tromp around town in, or you can't breathe. Her other dress didn't seem to fit into any of those categories, so I can only think of one last impetus for the costume change...