At the end of the bed sat a woman reading

“Perception is no more than successful hallucination.”
attributed to the AI scientist Max Clones

Emily awakens to a strange woman reading, at the foot of her bed. Chris Frith in his book Making Up the Mind: How the Brain Creates our Mental World gives the example of a lady named as Miss W whose experience illustrates how the brain is constantly making decisions about what we perceive based on probability rather than a stream of real information.

"One evening at dusk I went to my bedroom to fetch something I wanted off the mantelpiece. A street lamp threw a slanting ray of light in at a window, just sufficient to enable me to discern the dim outline of the chief articles of furniture in the room. I was cautiously feeling for what I wanted when, partially turning round. I perceived at a short distance behind me the figure of a little old lady, sitting very sedately with her hands folded in her lap, holding a white pocket-handkerchief. I was much startled, for I had not before seen anyone in the room, and called out, “Who’s that?” but received no answer, and, turning quite round to face my visitor, she immediately vanished from sight…."

In most reports of ghosts and visitations the story would stop here, but Miss W is persistent.

"Being very near sighted, I began to think that my eyes had played a trick on me; soI resumed my search in as nearly as possible the same position as before and having succeeded, was turning to come away when lo! and behold! There sat the little old lady as distinct as ever, with her funny little cap, dark dress, and hands folded demurely over her white handkerchief. This time I turned around quickly and marched up to the apparition. Which vanished as suddenly as before."

So the effect could be replicated. And what was the cause?

"And now being convinced that no one was playing me any trick, I determined to find out, if possible, the why and because of the mystery. Slowly resuming my former position by the fireplace, and again perceiving the figure, I moved my head slowly from side to side, and found that it did the same. I then went slowly backwards, keeping my head still unitl I again reached the place, when deliberately turning round the mystery was solved.
A small polished, mahogany stand near the window, which I used as a cupboard for various trifles, made the body of the figure, a piece of paper hanging from the partly open door serving as the handkerchief; a vase on the top formed the head and head dress, and the slanting light falling upon it , and the white curtain of the window complted the illusion. I destroyed and remade the figure several times, and was surprised to find how distinct it appeared when the exact relative positions were maintained"