It’s a mystery to her why none of the devices monitoring her had picked up that she wasn’t in a coma. Nobody knew that she had heard every word.

When I got to that part I was all, "Oh really? That's what they want you to think!" Then after a few more lines I decided that the actual outcome/twist was even better. But then a few moments after that I realized it could still go either way.

I'm curious about your writing methods, how far in advance do you plan out the story material? Do you just pour the words out and see what you created, or do you outline, revise, plan, plot, and devise ever so carefully where everything will go?