I know you are correct. But Anne's rep did initially say she was on a vent for a pulmonary injury. Of course, whether that was true or not, things can go downhill for anyone at any time. What I think was confusing-- or at least it was to me-- is that it was announced SO very quickly that she was expected to recover. After a wreck like that and fire, hearing that announcement so early was surprising to me. The eventual outcome wasn't, unfortunately, but it felt more unexpected given the early prognosis.
This is just a guess based on my medical knowledge. I think what likely happened is that they did not believe she was so injured that she couldn't recover. I know that sounds weird given how long it took to extinguish the fire, but if the early reports were accurate, I think she likely seemed not to be as injured as she was, at least on the outside. Then something else happened. This other thing could have been her blood clotting leading to a heart attack or stroke or some other cause of her heart stopping or even an internal organ injury they didn't discover initially. Once that happened, her prognosis took a major hit.