I think the line would make a lot more sense if she said she was going to destroy Kylo Ren. Then she gives into her anger and does almost kill him, which traumatizes her so much that she leaves for Luke’s island.
Mine is still in progress, but that’s largely how I’m planning on implementing it for my version. Kylo wants Rey to join him, she later reflects “He killed [his] father. I’m going to destroy him.” - setting up both why she still doesn’t trust him, and also (re)fueling her anger towards him for when they fight on the Death Star.