"It's great being back here," said Bill, looking around the chamber (Violet, the Fat Lady's friend, winked at him from her frame)." (GF31)
The Fat Lady’s best friend “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.
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).