Apparently in the book we start with Rey an Leia in Ajan Kloss. Leia training her with flashbacks of the time she trained with Luke.
After Rey finishes de training course she gets a vision of what Kylo is doing, the Mustafar stuff and flashes of the throne.
I like how this could look.
-Rey starts seeing this, we cut to Kylo killing people on Mustafar.
-Her reaction, cut to more visions of the throne
-Back to Rey trying to get back to herself and the BB8 stuff with the fallen tree.
End of the scene and then we cut to the aftermath of Kylo’s massacre.