But Jack's friend was. Kai knew this. She felt him roaming the island more than once. There were others, too. Things that shouldn't be. Sharing the island with her. And the Voice said to kill them all.
Kai had to fight herself from Hunting. She had to keep her distance from all of them. Hole up on a part of the island where none of them went. It wasn't really far enough for her liking, but she made sure not to roam, and kept herself calm.
First she built herself a little shelter. A small lean-to that would keep the sun off of her when she wanted, and hold back rain and wind if it came. Then it was stocking it. Food, wood, items she needed, and some she didn't. Like the pretty little rock that she found and thought Jack would like.
Kai had no idea about the second island. She never even made it over to that side of hers to see it. She was just sure that everything she cared about was gone, and she was surrounded by the impossible. Fending for herself. Trying not to slaughter everyone she was with.