She was intended to be voiced by the late Elsa Lanchester.
Elvira appeared in the original version of The Aristocats. In this version, Elvira is a maid who works for Madame Adelaide de Bonfamile who, much like Edgar Balthazar, Bonfamile's butler, wishes to inherit Madame Adelaide's fortune upon her passing, as she has no living relatives. However, given that Madame Adelaide wants her cats to inherit her fortune, Elvira and Edgar scheme together to get rid of the cats and inherit the fortune all for themselves, forming a Big Bad Duumvirate.
Elvira and Edgar were going to even have a song entitled "How Much You Mean to Me/Court Me Slowly", where Edgar attempts to propose to her so he can have access to her share of Madame Bonfamile's fortune, demonstrating how foolish and incompetent Elvira is when she fails to realize that Edgar is manipulating her and doesn't actually love her.
It's completely unknown what was going to happen to Elvira at the end of the story, but it's likely that Elvira would have left the story in a similar way to Edgar's.