"Émelie Isabelle Potter!" Émelie knew she was in trouble when her Maman used her full name.
"You need to eat your veggies"
Veggies are gross Émelie thought.
"Nuh uh."
"Émelie, sweetie did your Maman never tell you what happens to little Veela who don't eat their vegetables" Émelie's papa, Harry, gasped.
Émelie shook her head.
"No? You should tell her love." Harry said imploringly.
"Eet is a tale ze Veela have passed down for generations. Ze Tale of ze First House Elf" Émelie's mother, Fleur, paused for dramatic effect.
"For as long zere have been Veela, Mamans have told little Veela to eat their Veggies. But one little Veela, Victoire, refused. And slowly but surely she shriveled up. Her nose and ears grew to the size of an elephant's! And she stopped caring about her clothes!"
Émelie gasped! Stopped caring about clothes!?
"Maman! So Mipsy was a little Veela?"
"Oui, mon petite."
"And that's why we need to be nice to her?"
"Oui."
"OK. Papa I want the broccoli."
Tl;dr: Fleur scaring her daughter thinking she'll become a house elf if she doesn't eat her veggies