The story seems relatively clear to me. I would bet she had a visual of the story in her head, and her writing was more like reporting that vision. She just mis- or under- selected what to report on. Likely the book was about a magical vine, and the girl was drawn to it. The librarian's warning probably included something about it being a very special book. And when she read it she was so fascinated, she couldn't stop, despite remembering the librarian's warning.
My DS does that, because of his writing issues, but the full vision is in his head. Any mild questioning and he'll tell the epic context of his story.
