Scarlett knew from experience that, if Mammy’s curiosity were not immediately satisfied, she would take up the matter with Ellen, and then Scarlett would be forced to reveal everything to her mother, or think up some plausible lie.
Mammy looked at her piercingly, just as she had done when Scarlett was small and had tried unsuccessfully to palm off plausible excuses for misdeeds.
Prissy went off at a trot, the letter gripped in her hand, and Scarlett went back upstairs, trying to think of some plausible lie to explain Mrs. Elsing’s failure to appear.
Miss Melly will believe any plausible scoundrel.
There are no more uses of "plausible" in the book.