"You will regret this. This is the third and the last time I'm putting up with your bullshit. If you think I'm going just come crawling back to you, think again. Because to be honest, if you were twice as smart, you'd still be stupid. Fool me once, shame on you. Fool me twice, shame on me. But fool me thrice, hell will be unleashed on you. Goodbye, Ronald."
She never swears. Goody-two-shoes, Hermione Granger does not ever promote any bad vices. But as you can see, she herself isn't paying attention to her own rules. Want to know why? Find out on Revenge.