@/Threee
it's quite reasonable in my perspective. when smoke turns into a person and the guy moves, she should still be in shock or don't know what's happening at all. since the ml is unconscious, she didn't feel any immediate danger, so she's still trying to figure out what happened and why the man's here.
however, when the man wakes up and stared at her, she feels threatened because she doesn't know what the man will do next, and therefore she screams.
and, to most people, ghosts don't take human form (or at least not as neat or as "human" as the ml). it would be reasonable for the fl to think it's an intruder instead of a ghost.