I think it's wrong to put such blame on the child and her parents. My son has autism and ADHD, he can be VERY aggressive. My other children are not aggressive at all. I cannot control what happens when he is at school or nursery and it's really hurtful and horrible that people blame the mother.
The staff were responsible. If they know the child is aggressive they either need to suggest another establishment for the child or increase staff ratios to watch the child.
I think it's horrific what happened to that little girl and I would be livid too, but surely it's the nursery who are responsible?
I can't believe someone would expect police action to be taken against a 2 year old.