This chapter taught me something. Perversion has 1 condition for it to be not "bad" and that is for it to be accepted.
The duke is getting interested in her since she started acting spicy for him. But its bad perversion cause she doesnt accept it. But her intrigue by her feet being touched by another man is fine because theres no rejection.
So consent is all that matters. Either im enlightened or my lack of sleep is messing with me.