If it was actually the kid's fault, she'd be perfectly right to sue, I don't care if he's seven, or five, or three years old.
*SIGH*
A minor is a person who is not of legal age. How can you sue someone who is not have full legal rights? (And we're not talking about a crime committed here). Maybe--maybe--the parents can be sued if their own recklessnes is responsible for what a child does. This case doesn't warrant that, IMO.
When I was growing up, there was such a thing as an "age of responsibility". You expected kids to act like kids, because they didn't know any better. They were not accountable by the rules of adults, because they were not adults. It's really weird, how on the one hand personal responsibility is being sloughed off while on the other attempts are being made to hold accountable those who by their nature are not accountable.