]Also, note that Kitty was disconcerted when her father called them (his youngest daughters) "silliest girls" whereas Lydia was completely indifferent. There's a tiny difference there after all.

One must consider that Lydia basked in the nonwavering regard & affection of her mother, whereas Kitty is snubbed or ridiculed by both parents. I feel sorry for her as well as for Mary. They are certainly the two 'neglected' children in this family. :-{