Nobody on first. Mom’s responsibility she did nothing. Lufthansa’s responsibility to the other people who had paid good money for the flight; they did nothing. They should have dropped them off in Belgium before they crossed the Pond. And not ONE passenger complained? Boy, I would have.
The captain should never have taken off with an out of control demonically possessed brat on board. In the US, the captain can make that call and it’s not subject to questions.