Elizabeth asks Darcy how he ever fell in love with her. He points to her liveliness of mind, but, like Elizabeth, he can't put his finger on when it happened.
Elizabeth and Darcy change gradually, through careful reflection and self-improvement. This gives their marriage a solidity that Lydia's lacks.
Elizabeth writes to tell Mrs. Gardiner of her engagement, as does Darcy to Lady Catherine. Mr. Bennet writes to Mr. Collins who, along with Charlotte, soon return to town to congratulate the couple and steer clear of a furious Lady Catherine. Georgiana Darcy writes to Elizabeth of her happiness at having such a sister. Caroline Bingley writes empty congratulations to Jane. Jane sees through her shallow sentiments, but replies with a nicer letter than Caroline deserves.
The web of letters sent indicates how Elizabeth and Darcy's marriage affects everyone. The fact that the two most shallow and class-conscious characters—Lady Catherine and Caroline—disapprove of the marriage makes it seem like a true union of equals based on respect, love, and commitment.
Elizabeth tries to insulate Darcy from the foolishness of Mr. Collins, Sir William Lucas, and Mrs. Philips, but Darcy tolerates them pretty well. Elizabeth looks forward to hosting her close family at Pemberley.
Darcy's pride is tempered by his new humility. Elizabeth looks forward to sharing the new wealth she has gained.