The history of Daisy in animation can be traced to the appearance of her precursor Donna Duck in the cartoon short Don Donald (first released on January 9, 1937). The short was directed by Ben Sharpsteen. The plot had Donald courting Donna somewhere in Mexico. His efforts were frustrated and Donna leaves him alone and rides away in her unicycle by the finale.
The short is important for introducing a romantic interest for Donald. But one should note that Donna had little in common with Daisy other than both being female ducks and sharing a temper. Donna was more or less a female version of Donald both in design and voice. Her voice was provided by Clarence Nash and was a slightly higher version of that of Donald. Donna was not intended as a recurring character and the Donald shorts of the following three years featured no female companion for him.
Donna returned in Bob Karp's Donald Duck daily strips from 1951, where she's a Mexican lady moving in as Donald's neighbour, causing Daisy to be jealous. This contirutes to enstabilsh the two as separate characters, and marks the first time they appear together in a story.