Malfoy said some cruel things about Hagrid and it pushed Hermione off edge; first she drew her wand but after Ron called out to her she put it down, Malfoy then started laughing so Hermione turned back around and punched Draco. read more
In the book, Hermione Granger slapped Draco Malfoy, she only punched him in the movies. The slap occurred on page 216 (UK children's version), chapter 15 'The Qudditch Final'. read more