Cass didn't get to make Gideon do that because as soon as the dance finished, his Aunt and the other fairies were announced. That also meant that Cass was alone as his family entered the ballroom. No Edgar, not Gideon, just Cass, a glass of champagne, and a heat in his chest.
His Aunt and the other fairies hadn't dressed informally in the house when they were staying with him, but they hadn't dressed in their finery either. They had made themselves comfortable, as Cass would have expected of them.
Cass had a feeling that if they had arrived when he wasn't in a dungeon he might have seen them in the kind of finery that was greeting his eyes right now, minus the crowns and necklaces that declared their intent.
