Moomy was probably finally putting her hoof down and Chubley couldn't take it. I want to say "good for her" but if the kid is 10 and still putting up a fuss like that, she didn't do her job when he was younger. Even if the kid was autistic or something, there's still a difference between a meltdown (like the sounds in the store are too loud or the lights are too bright) and a tantrum.