I read it more as all the girls imaginary characters she thought up leaving her body. You know how sometimes to pass the time you just imagine a story and characters or think of a scenario in media you'd like to see happen?
I see it all as The girl was walking along imagining things, died, and all her imaginary characters managed to crawl out into the real world, and since they knew just as much as the little girl (aka pretty much nothing) they didn't understand anything bad happening to em.
I think the girl who didn't want to leave the corpse and Jane knew this however. Mostly because Jane was competent when she isn't against someone with a bigger forehead then her
, and the corpse girl had a nightmare of the little girl waking back up leaving all them trapped in her mind again.
In a way its like they gained free will but didn't have much actual character to them to learn and grow with that free will. Minus those like Aurora.
Also personally I found how dark this book was to be kinda hilarious. The absurdity of some of the deaths though others effected me more then others
Call me an edgefag all you want but we can both agree it was a great read