Grandma Hortensia "Hydrangea", who last name was presumably Gadwall, was an anthropomorphic duck.
Apparently born in 1818, Hortensia was the grandmother of Elvira Duck. Elvira even spoke about times when her grandmother took care of her more than her own mother did. She married to a man named Grandpa Gadwall.
Behind the scenes
Hortnesia, known in the original Portugese as "Vovó Hortênsia", appeared in the 1982 story, Um Natal do Passado (INDUCKS: B 820168) Here, she is shown to be the grandmother of Elvira Duck. It can be assumed that she is Elvira's maternal grandmother, and thus, a Gadwall.
A grandmother of Elvira Coot appears in The Grandma Duck Story (INDUCKS: I TL 1677-b). Presumably the same character as Hortensia Gadwall, this grandmother owned a farm and was remembered for burning a cake.