Quarry Sighted

What happens when a professional assassin transmigrates into an anorexic eighteen-year-old's body after being murdered, right when the new body is murdered identically? Complete an utter chaos of course. Natalie Dumas was on the verge of retirement. Unfortunately for her, she had a serial killer stalking her. In an alternate universe, the same was happening for Cora Sterling. A switch occurred for Natalie, but not for Cora, although her soul remained alive and aware of what was happening. Between the memories' confusion mingling, the souls should've merged. Still, only the memories did, and even then there were blocs, important chunks missing, that almost got Natalie killed anyway. The alternate Earth she'd fallen into was on the verge of severe natural cataclysms, none of which were avertable. As a result, Natalie now Cora, and two cousins she actually got along with, tried escaping via a ship. However, that was another twist because she'd wound up in a book setting, a book Cora wrote, but hadn't put into publishable format. What the heck is going on? Well, no matter what, they would survive one way or another, even if it meant reincarnation elsewhere, such as a Purgatoire waystation.