Angela's "Angel" *spoilers*
This is one thing we don't ever seem to hear much talk about regarding what happens.
In a few scenes, we see Angela drawing something in her youth. In a later scene, the woman at the convent calls it her Angel, but as Sandy explores the room, we see her unearth more drawings, as the childlike angel image, over the course of several dozen images, takes on a more horrifying look, of a more horrifying Version of "The Scream" in the image she takes with her.
What if Angela had some sort of guardian angel, that was twisted and deformed given her psyche, let alone the events of what happened?
It should be noted that during the killing of the others, Angela's form and body begins to transform. When she makes the first kill, she looks like she did in the cemetary when playing the game...but by the time she appears in the hallway to Sandy, she's lost all her hair, and is writhing about.
I do feel Angela was slightly unhinged, since she didn't seem at all happy when she first heard Sandy playing the game with the others as kids. As well, the sense of betrayal, intermingled with the "joke" that ended up putting her into a coma, probably caused the spirit to manifest.
"Thanks, guys." "So long, partner."
- Toy Story 3 (9/10)