An insult to Hermione's intelligence, however unintentional, is still a direct attack. It's finally time for revenge. She's got all the practice she needed.
[Set in Ootp] Inspired by this scene in canon:
And Hermione began to cry weakly into the back of Millicent Bulstrode’s robes. Millicent stopped trying to squash her against the wall immediately and dodged out of her way looking disgusted.