Scans_Daily

"The Problem of Susan" is actually a pretty old discussion of the Narnia books, essentially on wether or not Susan "deserved" to be punished by not being allowed in heaven, wether or not her path to heaven was supposed to be different than her brothers, etc.

Basically, this is Gaiman's take/response to "The Susan Problem". He is arguing that, rather than being denied heaven, she was able to survive Narnia and grow to be old . With The Professor representing a Susan who managed to grow into old age and die a peaceful death. (and that, if she had been punished by God, then it's more accurate that she had been betrayed)

The dream sequence is both Greta getting her answer to the question and representing The Professor's death.
Or it could be Gaiman being Gaima, who knows. he also wrote a story in which Snow White is a vampire.