It was probably more Calamity's work than hers. Her having cancer sort of made me feel a little better about David killing her. This may sound terrible, but I know that it is extremely painful to live with, as my grandmother died of Pancreatic Cancer October of 2013 and, as a loved one you can see that they are suffering terribly. Though I also felt that she kinda deserved that suffering after killing millions of people. It may have also been the reason she gained a touch of her sanity back as she no longer needed to fear death as she knew it was already upon her.