There were quicker, better, and easier ways to get a class than killing 57 people over a period of seven weeks. She is not like Black Knife either. She is not a sadist, and she doesn't enjoy killing people.
So whole thing was not enjoyable for her. He can't say she did it for fun. But she did it anyway. It makes her appear to be a lunatic.
Then there is also the fact that she simply unnerves him. It is almost as if she doesn't have emotions. She doesn't get angry, laugh, cry, smile, or grin. Her face is constantly calm, and her eyes are sharp.
Serial killing is not the only thing that doesn't give her pleasure. Practically nothing gives her pleasure. She simply does them for an unknown reason. It appears that she simply does them because she has to.
He mused to himself as he watched the fire, "She is like a robot stuck in a logic loop. She is unfeeling and uncaring, and I don't think it is because of God's Domain."