"She and her friend Violet drank their way through all the wine in that picture of drunk monks down by the Charms corridor."
-- Hermione's explanation for the Fat Lady password choice (HBP17)
Violet is a witch in a portrait hanging in Hogwarts. She is best friends with the Fat Lady, who calls her Vi.
Violet is a wizened, pale old witch whose portrait is located in the antechamber off the Great Hall (GF17). Having heard all the news about the Goblet of Fire choices firsthand, she rushes through seven staircases of portraits to the Gryffindor Common Room entrance to tell everything to her friend The Fat Lady.
Likes a drink and a gossip
Other canon notes and references
Violet winks at Bill Weasley when he and his mother visit with Harry before the third task of the triwizard tournament (GF31).