It was a small child so you want to ban them? You want to report the parents to child protective services and make her a ward of the State?
Literally thousands of people have been hit by foul balls over the years. Only a very few have resulted in serious injury and I believe there was one death at Dodger Stadium. I think more people have died from getting drunk and falling out of the upper level stands than have been killed by foul balls. Unfortunately “heads up” does not establish a protective shield.
MLB has mandated longer stretches of protective netting, most recently that all will extend at least to the far end of each dugout. It was reported that this child was in Section 111, which is just outside the extent of the netting- you can clearly see that in one if the pictures on line.