Tbf, she doesn't know anything. She doesn't remember her past life, what happened or how got teleported. She only remembers her Korean name, the happenings of the book and what caused her to die. Anyone who doesnt remember anything or what they are are sure to be fearful and anxious of what's going to happen. She read in the book that ML likes torturing and killing white hair people, should she not be scared when she herself has white hair??
She isn't very smart also. You can argue and say that she knows how to read, talk, count and can tell what each object's names are, but that's it. She doesn't have any life experience besides knowing how to be nice, how to run away and hide. You can't expect her to be confident until she learns how to be confident. She doesn't even remember her previous occupation, how do you expect her to realise that ML won't kill her when she is not even educated emotionally??
Of course, I completely understand your frustration. When looked in a different way, she seems almost stupid, borderlining on useless, and I agree. But she is MEANT be useless until she learns of her powers and strengths. That's my 2 cents tho, if you disagree that's completely fine with me too, please don't take this as a way of hate directed towards you as that's absolutely not my intention.
I mean, it's realistic. You don't really expect someone that doesn't remember ANYTHING to start off being a boss bitch. She doesn't remember how she got there, her name, her age, etc.
Doesn't MC realise that ML not gonna killed or mad at her.. From the start ML has been kind as an angel to her.. Everytime i see MC said something she always thought she was wrong and assume Ml gonna killed her.. Im tired seeing this