So, if I were her (young) and saw him at the dance, I'd be doubly upset because he had told me he "can't" like he was going to be out of the country at that time, had surgery planned for that day, or his parents prohibited dates, when that was clearly not the case at all. It's not that he can't, he just didn't want to.
Wow, I didn't mean it that way at all. But, it's good to hear that it could be taken that way. Hopefully the OP will figure out the best thing to say by the time we all weigh in. I do see what you mean now, on reflection.