I don't know how it would happen, but I have the most lovely imagine in my head, of Sith Lord Rey in all her majesty, and at her feet is her most loyal and devoted servant, Kylo Ren.

I would love it if she treated him almost like a pet, with affectionate touches, rewards for obedience, punishments for disrespect, etc. And Kylo loves it, because she's basically the best Sith since Vader.

(I don't know if that's what typically meant by petplay...hope I'm getting the idea across right.)