I dunno, I thought the attraction between Kylo and Rey was more of a "nice guy" situation. He kept popping up in her head so she thought maybe she can save him from the dark side and make amends for writing him off. Nothing romantic.
Ben, meanwhile, took her jumping into his head and trying to save him as "OMG A GIRL FINALLY LIKES ME, I SHOULD KILL MY BOSS AND WE'LL LIVE TOGETHER FOREVER AND EVER RUILING THE UNIVERSE AND PUMPING OUT LITTTLE SKYWALKER. ITS WHAT GRANDARTH VADER WOULD HAVE DONE.
So when the chance comes Ben kills Smoke, turns to Rey and gets a hard no. Then he looses his shit.