The Great Gatsby- Chapter 9

Catherine did not sully her sister's reputation by revealing her affair.

Catherine, who might have said anything, didn’t say a word. She showed a surprising amount of character about it too — looked at the coroner with determined eyes under that corrected brow of hers, and swore that her sister had never seen Gatsby, that her sister was completely happy with her husband, that her sister had been into no mischief whatever. She convinced herself of it, and cried into her handkerchief, as if the very suggestion was more than she could endure.