It is said nothing is more dangerous than a woman who knows she is gorgeous. She holds power over those around her, those who will bend and melt away in her wake. It is also believed people do not know they are evil. People are doing what they believe to be correct, but only to other people's perspectives is the act deemed good or bad. How can you know one, but not the other? If a woman is smart enough to know the power she wields, why is it automatically assumed she would not be aware of the evil inside her? There is "evil" lurking inside all of us.
You may come back with a word like 'Conscience.' What do you think it is? What do you think of vampires with gelled hair styles and a humanity switch being desperate to take the cure for vampirism?
Not having a conscience is not a prerequisite to being evil; you can simply ignore it and turn it off, just like a switch.