VIVIAN LEWIS: Why don’t you present Rory there?
EMILY: Oh . .. uh . . . Well, I don’t know. Isn’t it a little late?
SUNNY: Oh please. For Emily Gilmore, I’m sure they’ll bend the rules.
Generally you’d need to apply for a debutante ball several months in advance, and commit to a ten to twelve week course of dancing and etiquette lessons in preparation. It’s more than a “little late”, and they won’t be “bending” the rules for Emily Gilmore, they’ll be smashing them to pieces!
Naturally rules are only for mere mortals, not for the glorious Gilmore girls. In this case, it’s practical for the show, because it cuts down months of ball preparation (snigger) into less than two weeks.