Girls and Revenge

Harry was left to ponder in silence the depths to which girls would sink to get revenge.

— after Hermione's insinuation that she will be going to Slughorn's Christmas party with Cormac McLaggen because she likes "really good" Quidditch players (i.e. Cormac and Viktor Krum and... not Ron) (HBP15: The Unbreakable Vow)