Marietta Edgecombe

Marietta Edgecombe is a student at Hogwarts School of Witchcraft and Wizardry. She was sorted into Ravenclaw House and is a friend of Cho Chang, the Seeker for their House Team.

In Order of the Phoenix, Marietta accompanied Cho in joining Dumbledore's Army, despite her obvious suspicion of Harry Potter's intentions as well as his claims that Voldemort was still alive.

Due to pressure from her mother, who worked at the Ministry of Magic and for Dolores Umbridge, Marietta was led to betray Dumbledore's Army to the Ministry. She would, however, come to regret this when it was found that the piece of parchment Hermione Granger had everyone sign at the first DA meeting in the Hog's Head was jinxed, making anyone who betrayed them break out in pimples that spelled the word "SNEAK" across their forehead. When mentioned on the Hogwarts Express on the way to school it is noted that her thick layer of makeup does not quite obscure them, leading us to believe that no counter-jinx was ever found. Eventually the pimples faded, but left a few scars.

So that she could not implicate Albus Dumbledore and Harry, just before she was to confess all, Kingsley Shacklebolt, an Auror and a member of the Order of the Phoenix, obliviated her.