Adelaide is presumably a female anthropomorphic dog.
Description
This aunt of Goofy (either on his father or mother's side) owned an antique coffee grinder of which, for reasons unknown, Goofy owned a projector slide of that coffee grinder, which he mixed up with his windmill slides at a "lecture" Goofy gave on the history of mills.
Behind the scenes
Aunt Adelaide was mentioned in the 1987 story A Goofy Look at Mills.