To get Caroline Bingley's character right, you have to understand that she is a foil for both the Bennet sisters and Mr. Darcy.
She is the more rational choice for Darcy vs. the Bennets. She has education, manners, a fortune, and clearly, relatives that he likes. So many fan fiction authors make her vulgar and/or unfashionable, but she isn't! That is why Darcy enjoys hanging out with her in the beginning; he would not have her at his house if she was embarrassing. Even when angry with Elizabeth, Caroline does not dare go further in attacking Elizabeth at Pemberley. She has self control. She understands boundaries, which Jane and Elizabeth mostly do, but the rest of the Bennet family struggles with. This is why she's a foil for them.
As for Darcy, at the beginning, Caroline is a nearly perfect mirror of his opinions and snobby attitude. She is doing this on purpose as a way of flirting, but it's probably pretty close to her real personality anyway. She's right that Darcy looks down on Elizabeth's uncle being a lower class lawyer. She's right that he finds the Bennet family intolerable to marry into. However, as Darcy falls in love with Elizabeth and then reforms, Caroline's mirror distorts. That shows his growth in the novel. She, like Elizabeth, fails to update her priors, though to be fair to Caroline, she didn't build her knowledge of Mr. Darcy on first impressions. It's harder to change her mind because she did once know him very well.
Side note: this is also why people woobyfying Darcy hurts Caroline as a rational character. They start in a very similar place and love mean girl gossiping together, then he changes. When Darcy's flaws are erased, it makes Caroline look super irrational and much crueller.
Lastly, Caroline is above all else, pragmatic and strategic. She does not hold grudges once it becomes more advantageous to drop them. She would never, ever, now that she is connected by marriage to the Bennets, mock them in public. Because that reflects on her! Caroline would be in London talking up that the Bennets are a very old gentry family with an ancient estate or something. She's going to be giving them a PR makeover to all her fancy friends because they are HERS now, for better or for worse and whether she likes any of them or not. Yes, in private she might be mean, as she is in the novel, but again, she's not vulgar and she has nothing to gain in public. She has manners, she has self-control; being a mean girl doesn't override that.
#gotta point out that while I absolutely love the scene where Darcy shuts Caroline down#(every time I watch the 1995 show zrayak yells ‘GET REKT CAROLINE’ at the tv it is SO funny)#he’s specifically shutting down something that they used to do together#she reminds him that he said ‘I’d as soon call her mother a wit’ because HEY REMEMBER HOW WE USED TO DO THAT?#REMEMBER HOW FUN IT WAS? THAT THING WE USED TO DO ALL THE TIME?#like imagine if your main bonding activity with your bestie was getting drunk and watching bad movies and making fun of them#and then one day your bestie starts dating a screenwriter and NOW every time you bring up bad movies you get shut down#'oh no we shouldn't mock other peoples' hard work! that would be mean! :('#my brother in christ we watched the room (2003) & you said it was the dumbest thing you'd ever seen in your life what are you TALKING about#jane austen
Exactly! (tags from @bemusedlybespectacled)
Darcy is rejecting the self that he used to be as much as he's shutting down Caroline.
Love the idea that Caroline becomes the Bennets’ fiercest defender and PR manager—not because she’s had some miraculous change of personality and stopped being the mean girl, but because those monkeys are her circus now, dammit, and like hell is she going to let them drag her down. If anything, she’s going to become more manipulative and scheming than ever, but it’s for the benefit of these idiots.
Exactly! It doesn't take any change of character, she defends her own and marriage is forever. The Bennets are now her own! And she will defend Jane too for the same reason (so many people are like, "Poor Jane has to live with Caroline." Jane will be fine.)
I wrote a sequel to Pride & Prejudice once and Caroline was encouraging Kitty during her first season in London. People said I was writing her way too nice for canon, but Kitty is one of hers now! A good marriage for Kitty is a good connection for Caroline. It's self motivated and exactly in character.
