Warning This Section Does Contain Spoilers
This letter is from the desk of Dr. Harold G. Oliver M.D. He is treating Isabella while she is in her "body-without-soul" state. He makes the comment that the grandmother, Grace, seems content to let him do his work unimpeded. He seems to think that Bella will not wake up any time soon and will be in this state for some time.
The doctor's memo has a hidden message in the colours of the document. The most used two colours are blue and yellow, which of course make green. Reading the green portions of the letter reveals a message of:
Steady hold on her condition. I do not expect her to recover.