Remember the beginning, when there was a horrible snake eating the world? I believe Alice is that snake. When she dies, she rises out of her corpse anew, like a snake shedding its skin. She wanted to find her "brother" which is the book, so she must have been a snake in a book, too. She knows of all the horrible things that people desired when she consumed their souls and flesh and wants to return to the real world to consume more souls for their desires. It also explains how she ate those big cakes so fast and without trouble.