- "Greengrass, Daphne..."
- —Daphne being called up to take her O.W.L.s
During her school years, she was part of Pansy Parkinson's "gang" of Slytherin girls, and shared a dormitory in Slytherin Dungeon with Pansy Parkinson, Lily Moon, Millicent Bulstrode and Tracey Davis. She was a member of the short-lived Inquisitorial Squad in early 1996 and took her O.W.L.s in 1996 at the same time as Hermione Granger. She has a younger sister, Astoria Greengrass, who eventually married Draco Malfoy She has a nephew, Scorpius by this marriage.
In the spring of 1996, Daphne was one of the members of the Inquisitorial Squad, formed by then-Headmistress Dolores Umbridge. She was one of the students that saw Fred and George Weasley flying away from school. At the end of the school year, the Inquisitorial Squad was disbanded after Albus Dumbledore returned.
During the last months of her seventh year when Voldermort took power over the school, Daphne was one of the Slytherins to refuse to practice dark magic. The Carrows punished her for her refusal, and was placed in the dungeons for a few hours. When Harry Potter returned, Daphne chose to fight against Voldermort and his army.
She held a disregard against Pansy who refused to fight and chose to deliver Harry to the Dark Lord. Pansy remained hidden while Daphne and Tracey fought in the Battle of Hogwarts. While Daphne was defending the hall, Tracey was immediately killed by one of the Death Eaters. Daphne avenged her friend's death by creating a spell to allow her to escape with Tracey's body. After the battle ended, Daphne placed Tracey's body with the others. She was later seen talking with Millicent Bulstrode after the war ended.