I'm voting on clone I have a pretty long theory, but two quick thoughts are it would explain why Rey has no notable parents and would also explain that scene in TLJ when she snapped and all of her mirrored selves snapped too.
But who knows! I just can't imagine Rey falling to the dark side and them showing us in the trailer, it's a bait and switch if anything. Heck, it could even be a vision like Luke in the cave on Dagobah or something created by Palpatine's spirit.
We'll have to wait and find out!