He came to the rescue at this point, and said in a consolatory and complimentary voice, "Camilla, my dear, it is well known that your family feelings are gradually undermining you to the extent of making one of your legs shorter than the other."
There are no more uses of "undermine" in the book.
Show samples from other sources
Her father had a way of undermining his sister’s lectures on the innate superiority of any given Finch: he always told his daughter the rest of it, quietly and solemnly, but Jean Louise sometimes thought she detected an unmistakably profane glint in Atticus Finch’s eyes, or was it merely the light hitting his glasses?
Harper Lee -- Go Set a Watchman
He cocked his head, trying on his "I’m so wholesome" routine, but his bloodshot eyes undermined his efforts.