Mystery of Actress in Blondie Takes a Vacation?

Movie girl: The series is very entertaining and I really like all of the films. I was wondering about one of the films. I think it was Blondie TAkes a Vacation. AT the end it says the actress on the switchboard filling in for Blondie was Elspeth Dudgeon. I am a fan of hers, but I could have sworn it was Gertrude Hoffman from my favorite TV Series, MY Little Margie. The looks and even her distinctive voice was similar. I had seen Elspeth in The Old Dark House, but Gertrude in a variety of films. Does anyone have a clue? Both ladies were very gifted and a great part of the Golden Age of FIlms.

Thanks!