Ok, let's assume a suit against the kid is successful. When the woman wins a judgment against the 4-year-old, the kid will not pay, and it's only going to be good for 10 years at which point the plaintiff would be 97 years old.
Good luck collecting on that.
This is just one reason why, in a reasonable society, parents are sued for the negligent actions of their kids. Negligent supervision is very easily proven.