So, the main issue here for me is how the brain develops an identity, and the fact that in DID there presents fragmented parts of that identity that may develop into distinct identity states. Everyone has different states of consciousness, right? What is significant in dissociative disorders, and DID especially, is additional states that do not require additional substances (like alcohol) to develop, whether temporary or permanent. There is significant falsified research that tells us that memory formation is dependent on the state of consciousness you are in at the time (there are other memory formation factors, as well, like mood and environment, but it's irrelevant in this particular context). When someone gets "black-out drunk", and they don't remember anything, it's not because they weren't forming memories, it's because they are no longer in that state of consciousness. This means that the brain is designed to deal with trauma and stress with how it encodes memories. This is not unique to dissociative disorders.
A lot of development happens prior to birth. Even babies have sophisticated unconscious and conscious learning mechanisms. There's a ton of research showing that babies know not only that they are human (in that they recognize other human beings as their kind, vs recognizing that a dog is not their kind and being interested in it in a curious way), but also can tell when other human movements are social (waving at each other) or non-social (throwing a ball). Prior to age 3, children develop the concrete self, which is not based on memory. Things like that they are a child. A human. Small. These are things that, in effect, we are born to properly develop unless there is a severe neurological problem.
We do not start developing the remembered self until after this, when we start to understand that not only can we feel bad or good, but other people can be bad or good. This is about the time when splitting (black and white thinking) and dissociative disorders start to develop. In early childhood (around ages 3-7) the brain has not yet learned to integrate the identity states of others (splitting) and the identity states of the self (dissociative disorders). When trauma and severe and extreme distress occurs, this becomes a defense mechanism, and the brain never integrates these identities (others and/or self) to protect itself from damage. Cortisol, the stress hormone causes damage to the brain's functioning. This lack of integration to keep traumatic memories hidden in inaccessible states of consciousness is a part of the inherent will to survive.
So, my issue with this idea that children will think of themselves as characters, use their imagination, etc, etc, doesn't make sense. By the time this disorder develops, the child is cognizant of the fact that they are human. They also do not consciously create the identities, rather the states themselves are the catalyst for any fragments of the whole identity, and the process is a completely unconscious one that occurs naturally by design to protect brain function and long-term survival.
Anything else is delusion, and you can find several of these fantastical and illusional dissociation and depersonalization/derealization symptoms in literature on schizophrenia and other traumatic brain injuries that cause Oneiroid syndrome (which Nan might actually be experiencing due to her actual traumatic brain injury).
