Definitely, she should receive all the mental health treatment possible. In prison. It shouldn't be innocent by reason of insanity, it should be guilty by reason of insanity, and they should have double the bars on the jail cell because of it.
People that we might typify as evil are insane. Then again, have you ever met anybody in your life who wasn't insane? Or evil, for that matter? It may be relative, it may be a matter of perspective, but bottom line, people are just awful to one another, and everything else. And everybody is a bit wacky in their own way. That's what defines their personalities, how their kookiness differentiates them from other people's kookiness.