Edna is or was a female anthropomorphic duck.
Edna is or was the mother Webbigail Vanderquack, whom she for some reason was unable to care for by 1987 (at which point Webby's grandmother Bentina began caring for her).
Behind the scenes
Edna is mentioned in the French dub of the 1987 The Treasure of the Golden Suns.
Where she falls on a Duck family tree is an extremely thorny matter; while one might expect her to be the daughter of Bentina Beakley having married a Mr Vanderquack, this fails to account for the fact that one of Webby's parents is a sibling of Daisy Duck's. A possible way to resolve the matter would be for Webby's father to have been Edna Beakley's first husband only for her to remarry with a Mr Vanderquack whose name Webby took.