JA gives us very little of Kitty's speech, so I haven't had much luck distinguishing any particular voice.

Her speech is a bit self-centered, but not as much as Lydia's. It doesn't come across as very sophisticated, except perhaps the line "I do not cough for my own amusement" (chpt 2). Generally her wording is simple "good" (chpt 41), "more too", (chpt 41) "behave better" (chpt 49), "that tall proud man" (chpt 53).

Kitty reminds me of her mother in the line "La" (when exclaiming over Darcy's appearance in chpt 53), but that's only one case.