"Your Grace's world and ours do not mix," she said dryly.
"They do here at the Gardens," he pointed out. "Why not elsewhere?"
When Kitty is put into danger, it is decided that the safest place for her is with the Duke and his family ... at least until the threat is taken care of. The family is aware that Johnny believes Kitty might be "one of them" so they agree to keep her safe and treat her well and, just maybe, teach her about how to be a member of Society. It is all overwhelming, to say the least. Of course, the most overwhelming part is being in such close proximity to Johnny almost constantly.
And one thing leads to another, which leads to several more, which leads to ....
Read. The. Book.
(All of them. In order.)