In the TV show Columbo was Mrs Columbo a useful fiction invented by the detective and the odd occasion that other characters claim to have seen her she was perhaps a paid
Columbo: Ruhe sanft, Mrs. Columbo - Filmkritik - Film - TV SPIELFILM
Mrs. Columbo - Wikipedia
Mrs. Columbo - Rotten Tomatoes
Mrs. Columbo (TV Series 1979–1980) - Episode list - IMDb