Her disappointment in Charlotte made her turn with fonder regard to her sister, of whose rectitude and delicacy she was sure her opinion could never be shaken, and for whose happiness she grew daily more anxious, as Bingley had now been gone a week and nothing more was heard of his return.
There are no more uses of "rectitude" in the book.
Show samples from other sources
Mr. Cunningham, a man of uncompromising rectitude, had given her a pint free of charge for having guessed his name yesterday, one of the tiny things she adored about Maycomb: people remembered their promises.
Harper Lee -- Go Set a Watchman
Now I sat down to write a different kind of letter, one that tried to convey how much she meant to me, how much she had taught me, how I wanted to emulate her rigor and rectitude, how much I loved her and missed her.