Quote 58
Gran is dead. Having a picture of her won't change anything. (17.23)
This seems pretty cold, but once we know about the Liars' deaths, we understand why Cadence would want to get rid of reminders of dead people.
Quote 59
"If I die," I say as we look at the view, "I mean, when I die, throw my ashes in the water of the tiny beach. Then when you miss me, you can climb up here, look down, and think how awesome I was." (45.5)
Here we have the living telling the dead what to do with their ashes when they die. Cadence's memory is dead, and the Liars' memories are alive. Memory is all they have—or rather, all they are.
Quote 60
"You have no idea what it feels like to have headaches like this. No idea. It hurts […] It makes it hard to be alive, some days. A lot of times I wish I were dead, I truly do, just to make the pain stop." (49.37)
Mirren, Johnny, and Gat died horrible, painful deaths, but at least their pain was finite. Cadence has to live with hers forever.