I really want to see a fic like this, though I can't quite think of why f!Kylo would need to hide her gender. Maybe she feels people respect/fear her more when they think she's a guy? Maybe it's to hide her real identity as General Organa's daughter? Maybe it was Snoke's idea? I honestly don't know why, I just love this trope and I feel like Kylo is perfect for it, with the mask and all the layers to that outfit.

+Her real name is either Beru (for Luke's aunt) or Breha (for Leia's mom).
+She still unmasks for Rey, only Rey is in for a bigger surprise this time.
+If you want to make it shippy, I'm a fan of Rey/Kylo and Hux/Kylo, though other pairings are fine, and so is gen.