I think she was pretty tough. She was certainly tougher than a lot of the parents on this show. She continually called the cops on him. She didn't want to believe that he had killed her but really what parent does? She is doing what she can to make sure he never gets out of prison.
Also, I don't think it was any kind of idea that he was some angel and it couldn't possibly be him. She knew he was trouble, she just didn't want to believe he had gone that far .
True, she did seem pretty tough and under no illusions about his mindset. I can't remember if he was a diagnosed psychopath and born that way, or what. Now that I think about it, he probably was, and there's nothing she could have done to change it.
I just get cynical because it's natural to paint yourself in the best light on national television. I never hear parents saying "Yeah, I spoiled him rotten and gave in to his tantrums because it was easier. I didn't want him to suffer any consequences and refused to hear any criticism. "