I didn't get it. Can someone please...

A little girl at the hospital was getting molested/raped which eventually led to her rape and murder and disposal of her body in the hospital furnace/crematory. She had apparently tried to tell various people about her abuse like the nurses who either didn't care (WTF?) or didn't believe her and just let it carry on until her death. Her spirit or whatever was then trapped inside the hospital and decided the perfect timing for her revenge would be during a graveyard shift during blackout which, coincidentally was the first shift of a young woman that was also abused when she grew up in a children's home.

The dead girls spirit/ghost possessed the new nurse's body to conduct her revenge.

What I didn't get was why the ghost made the nurse stab herself, threw her through a window, general harm etc when we find out from the Indian girl that "she doesn't want to hurt us".