Have you forgotten the duel against Kylo in TFA where Rey willingly opens up to the Force to defeat him. Then she stalks him like a predator after injuring him and is even willing to kill him if the ground didn't split up and separate the two. JJ confirmed in his commentary that he did this because otherwise Rey would kill him. And the novelization said that an evil voice was telling her to do this. Then in TLJ, we flat out hear Luke say that she didn't even try to turn away from the darkness and that it calls to her. And Kylo's vision that she will turn to the dark could align with what we've seen of Dark Rey.
