I have to agree with the other commenter regarding vengeance being very big part of American society. I think part of it is likely also the severity of pain her daughter likely suffered during the attack. If this was the result of an accident or potentially a more immediate death for her daughter, I’m not sure the desire would be as strong. In the article she mentions as much, but I truly cannot imagine how it must feel to know that your child was essentially tortured to death. Regardless of how long it lasted, she likely died in pain and in terror. I can imagine that her mother thinks the perpetrator should not be granted a potentially peaceful natural death. I’m not saying it’s right, but I think it’s relevant to note that it wasn’t just a matter of immediate death.