...to whatever her stand-in for his library is; and Kitty is imitating her mother by closeting herself away (and perhaps reworking all the bonnets Lydia left behind). The younger girls really are selfish (and helpless in terms of dealing with crisis), but do we have any evidence they change markedly when Lizzy and Mrs. Gardiner return?

It is not surprising that the eldest daughter takes charge in her parents absence; running a household is what Jane has been training for all her life, and no doubt she would be good at it just as she was managing the young Gardiner children. We have already seen enough to surmise that Kitty, like Lydia, did not wish to follow her elder sisters' direction, and Mary was more interested in philosophizing conspicuously on a situation than in dealing with it.