I very much suspect that either Lizzy, who was concerned about Jane looking tired, or Mrs. Gardiner, who does not seem to brook much nonsense, let Mary and Kitty know that they were expected to help out. I think the aunt who tried to talk some sense into Lydia on her wedding day would be just as likely to tell her other nieces they had to pull their weight. I know that's just speculation on my part, but I would have liked to hear the conversation that no doubt took place.