I think what happened was that Dan Oh was supposed to get better post-surgery……since the surgery never happened there was a gap between what was intended and what was happening….you imagination and your intention sort of not logically getting along in your brain so Dan Oh kept feeling sick in the shadow because in her version of the world, it was something that was unreasonable….once she died in the shadow and her awareness died, that conflict between her aware self and writers imagination and intention resolved