I'm leaning in favor of the Parent on this one...I've met a few F/A's (inc. one particularly nasty F/A on XJet) who were super-rude to her Pax.

BUT. Saab also has a point - If I acted out or wouldn't shut-up as a kid, my parents held no reservations in shutting me up - forcefully if required LoL. I see kids in the terminals and aircraft getting away with murder. The mother in this case may have been the "victim," but she sure as hell wasn't "right."