"'That idiot Amanda,' Hortensia said, 'has let her long hair grow even longer during the hols and her mother has plaited it into pigtails. Silly thing to do.'"
If there is one thing Miss Trunchbull - headmistress of Crunchem Hall - can't stand, it's pigtails.
As Hortensia implies to Matilda and Lavender, Amanda Thripp should know this. But her mummy likes pigtails, so Amanda allows her to plait them. It's not Amanda's mother that has to face the wrath of the Olympic standard hammer-throwing pigtail-hating headmistress though... Poor old Amanda.
From 'Throwing the Hammer'
My m-m-mummy thinks I look lovely, Miss T-T-Trunchbull.