Kitty's reformation might begin with the removal of Lydia's influence. However, at this point her attitude towards her younger sister probably has a different orientation. In order to prevent such events as the "elopement" happening again, Kitty will have far less freedoms than she is used to enjoy.

I think her attitude towards Lydia at this point would be (to use modern vernacular):

"You ran off and had fun, but I got grounded."