I have spent A LOT of time thinking about a similar scenario.
Because how intense are the reunion going to be between them, after he has gone to the dark side and they finally meet again? She was just a little girl when he turned – so none of his anger would be directed at her. She would just be this thing that he loved that he had to sacrifice (give up, I mean, not kill) in order to follow the path he felt compelled to follow.
And so it’s not like it is with Han or Leia, because of course he still loves them but there’s issues and resentment and blame. But with Rey, there’s none of that. Just uncompromised love.
And if they had been close like siblings (or an AU where they are siblings), then her love might be unconditional. She would hate what he had become but she wouldn’t be able to just give up on him, especially if, like Leia, she firmly believes there’s still light in him.
I have two ideas/”scenes” I keep playing out in my mind. The first is where they haven’t seen each other since he left, and it has been years. And neither one of them expects the other to be there, but she catches sight of him. And he’s in full “apparatus” but she knows it’s him (because everyone knows it’s him), and so she’s scared and sad and fascinated all at the same time. But she doesn’t want to take chances and so she doesn’t confront him that time Because she doesn’t know for a fact that he won’t hurt her. She’s pretty certain but there’s still a little doubt.
And then maybe KR/Ben are in a duel with Luke, and maybe Luke is on the verge of striking a killing blow and Rey intervenes to save Kylo, but then Kylo takes the opportunity to go after Luke, and so Rey puts herself between them. And Kylo doesn’t know what to do because he has no interest in hurting her.
That would all be prior to her having any kind of Force awakening or training.
If after, I could see her fighting him, saber to saber, just to get a chance to talk to him.
I have way too many ideas for this. It might become some kind of original novel, because, and actually I think I mentioned this somewhere else on the blog, but I always had this original fiction idea for a story about a brother and sister who have to face off against each other. He’s bent on world domination or whatever and she’s the only one who can get close enough to kill him, either because of special abilities that run in their family or simply because he wouldn’t kill her on sight. And she’s been trained and trained for a long time and everyone, all the hope, is invested in her, and then when the moment comes, she’s right there about to plunge the dagger into him (or whatever), she can’t do it, even though she knows it means that “evil” will win, and that she’s probably also forfeited her own life. He, in turn, can’t do it either even though everyone in his circle has told him that he has to get rid of her because she’s the only real threat against him and his only weakness. <3333
All the stories I’ll never write!
I’m super bummed that I’ve all but entirely convinced myself that Rey was never one of the new Jedi (reasons for that here), because Kylo killing all of the new generation of Jedi (including kids), but not being able to kill his little cousin Rey is – *crying* – so beautiful, with him stashing he away so that she won’t be a threat to him but doesn’t have to die. Kylo sparing the one person should have killed because of the future danger she posed. Kylo even saving her from one of the other Knights of Ren. Gosh, that’s the stuff.