“Mummy Diller” was a human woman who is now an undead mummy.
Description
A shot of Mummy Diller materialized on the ghost-to-ghost television channel in 1952 while her daughter, the witch Phyllis. She was, by then, a ghastly-looking undead mummy, though she nevertheless remained, as her daughter put it, "a real fashion nut", tastefully choosing her lipstick and what wraps to wear. She had a married a monstrous bellringer described by Phyllis as "a real swinger".
Phyllis also referred to Madam Mim as her mother; assuming that Mim is indeed a last name (or at the very least not just a first name), this would suggest that Mummy Diller is Madam Mim's sister.
A third sibling can also be deduced in the form of Medusa, also an aunt of Phyllis's, as while both Mummy Diller and Mim could plausibly hail from a Greek-oriented ancient world, the same cannot be said for bellringing Daddy Diller.
Behind the scenes
Mummy Diller appears briefly in the 1972 The Mouse Factory episode Spooks and Magic. The Internet Movie Database claims she was portrayed by a certain Jeanne Baker.