Miss Bingley and Mrs Hurst work to establish a friendship with Jane, and they allow that her sister Elizabeth is okay to socialize with as well. They are pretty much horrified by Mrs Bennet and the younger three sisters, however. Jane seems to like both of Mr Bingley's sisters just fine, although Elizabeth can't really stand them because they consider themselves so superior.
Charlotte Lucas on love and flirtation
Now, we've already established that Charlotte is an intelligent, pragmatic sort of woman with a keen sense of observation. She is also seven years older than Lizzie, who we will learn is twenty somewhere in Volume II. (I don't consider the main character's age to be a spoiler, do you?) We can therefore assume that Charlotte has a somewhat better understanding of the workings of the world than Lizzie does, even if we don't agree with all her opinions.
When Lizzie tells Charlotte that Jane seems to be in the early stages of falling in love with Bingley, she also mentions how happy she is that it's not blatantly obvious to everyone around them. Charlotte begs to differ:
". . .[I]t is sometimes a disadvantage to be so very guarded. If a woman conceals her affection with the same skill from the object of it, she may lose the opportunity of fixing him; and it will then be but poor consolation to believe the world equally in the dark. There is so much of gratitude or vanity in almost every attachment, that it is not safe to leave any to itself. We can all begin freely -- a slight preference is natural enough; but there are very few of us who have heart enough to be really in love without encouragement. In nine cases out of ten, a woman had better show more affection than she feels. Bingley likes your sister undoubtedly; but he may never do more than like her, if she does not help him on."
On the one hand, I'm pretty certain that most of us laugh at Charlotte along with Lizzie; on the other, if you stopped that quote before the "In nine cases out of ten" line, I'm pretty sure most of us would agree that there is a lot of truth in Charlotte's words: they might move from regular conversation to flirtation, for instance, early on - but without actual encouragement from the other party, most people move on, figuring the other person is uninterested.
Charlotte's end point is that Jane is so reserved that, given the limited amount of social action she and Bingley have together, he might not realize that she likes him, since he can't come to realize how reserved she actually is to realize that her showing any preference is quite a big deal. You can sort of hear the troubled string music starting under Charlotte's words, if you listen carefully to this particular passage - another example of foreshadowing done so very well that some people don't realize it's here.
Speaking of foreshadowing, let's look at Charlotte's and Lizzie's final exchange:
"Well," said Charlotte, "I wish Jane success with all my heart; and if she were married to him to-morrow, I should think she had as good a chance of happiness as if she were to be studying his character for a twelvemonth. Happiness in marriage is entirely a matter of chance. If the dispositions of the parties are ever so well known to each other, or ever so similar before-hand, it does not advance their felicity in the least. They always contrive to grow sufficiently unlike afterwards to have their share of vexation; and it is better to know as little as possible of the defects of the person with whom you are to pass your life."
"You make me laugh, Charlotte; but it is not sound. You know it is not sound, and that you would never act in this way yourself."
To which I (and possibly Charlotte) say: "Oh really?"
Meanwhile, let's look in on Mr Darcy's thoughts, shall we?
Whereas Lizzie has dug in her heels with respect to her initial impression of Mr Darcy, he has found himself somewhat mortified to discover that his rather ungenerous assessment of Lizzie is changing - and that despite his initial antipathy toward her, he finds her rather attractive after all.
Occupied in observing Mr Bingley's attentions to her sister, Elizabeth was far from suspecting that she was herself becoming an object of some interest in the eyes of his friend. Mr Darcy had at first scarcely allowed her to be pretty; he had looked at her without admiration at the ball; and when they next met, he looked at her only to criticise. But no sooner had he made it clear to himself and his friends that she had hardly a good feature in her face, than he began to find it was rendered uncommonly intelligent by the beautiful expression of her dark eyes. To this discovery succeeded some others equally mortifying. Though he had detected with a critical eye more than one failure of perfect symmetry in her form, he was forced to acknowledge her figure to be light and pleasing; and in spite of his asserting that her manners were not those of the fashionable world, he was caught by their easy playfulness. Of this she was perfectly unaware; -- to her he was only the man who made himself agreeable no where, and who had not thought her handsome enough to dance with.
He began to wish to know more of her, and as a step towards conversing with her himself, attended to her conversation with others.
Elizabeth, acting on her own perverse sense of humor, verbally jousts with Mr Darcy in a way that he is completely unused to - he's used to sycophants like Caroline Bingley, who are throwing their cap at him because he is tall, handsome and filthy rich. Having someone like Lizzie banter with him without seeming interested in "catching" him is a complete breath of fresh air for him, increasing her appeal (without her realizing that he finds her in any way appealing at all). Without realizing it, Elizabeth has stumbled onto Mr Darcy's preferred method of flirtation. It's all so very amusing to us as readers (and to Charlotte Lucas, I believe, as well), as we sit and watch them strike sparks at cross-purposes.
Charlotte presses Lizzie to play and sing for the company, and although she does neither exceptionally well, she doesn't exactly suck, either. Plus she's attractive and spirited, and therefore makes a good impression. Mary, her next younger sister, takes her place at the keyboard. Poor Mary: "in consequence of being the only plain one in the family, worked hard for knowledge and accomplishments, [and] was always impatient for display." After showing off with a rather ambitious concerto (probably played okay technically, but lacking any true musicality), the youngest Bennet sisters (Kitty and Lydia) press her into playing songs so they can dance.
Mr Darcy is rather aghast that the evening, which was supposed to be filled with conversation and light entertainment, has turned into something approaching a Regency hootenanny. He's shocked out of his musings on the lack of culture displayed by Elizabeth's younger siblings by the kind (but overly officious) Sir William Lucas.
"What a charming amusement for young people this is, Mr Darcy! -- There is nothing like dancing after all. -- I consider it as one of the first refinements of polished societies."
"Certainly, Sir; -- and it has the advantage also of being in vogue amongst the less polished societies of the world. -- Every savage can dance."
Mr Darcy tells Sir William that he tries whenever possible NOT to dance, so Sir William does what people like Sir William do - he tries to get Mr Darcy to dance. With Elizabeth. Who is having none of it. So of course Darcy is all "No really, I'd like to dance with you," which pushes her to the "Sod off, I don't need your pity" place, and it's all completely wonderful.
And then, while Darcy is musing on how charming Elizabeth Bennet is, Caroline Bingley swoops up to him and assumes that he's pondering how horribly tedious the whole evening is, only to have him tell her that he's thinking how attractive a pair of "fine eyes" can be. Caroline (who would reallyreallyreally like to land Darcy for herself) fishes to find out who the young lady might be, and you can almost hear her deflate like a punctured soufflé at his (and I point this out on purpose) exceedingly honest response: "Miss Elizabeth Bennet."
"Miss Elizabeth Bennet!" repeated Miss Bingley. "I am all astonishment. How long has she been such a favourite? -- and pray when am I to wish you joy?"
"That is exactly the question which I expected you to ask. A lady's imagination is very rapid; it jumps from admiration to love, from love to matrimony, in a moment. I knew you would be wishing me joy."
"Nay, if you are so serious about it, I shall consider the matter as absolutely settled. You will have a charming mother-in-law, indeed, and of course she will be always at Pemberley with you."
He listened to her with perfect indifference while she chose to entertain herself in this manner, and as his composure convinced her that all was safe, her wit flowed long.
A few things to note in this exchange: (1) Again, Darcy was completely honest with Caroline about what he was thinking and who it related to; (2) Darcy's comeback about how quickly women imagine a happy ending is pretty darn hilarious (and again, based in truth); (3) Darcy has unwittingly drawn a huge target on Elizabeth with respect to Caroline, as Austen makes clear when Miss Bingley "immediately fixes her eyes" on Lizzie; (4) He does nothing to dispute Caroline's opinion that Mrs Bennet is atrocious; and (5) In this instance, he does absolutely nothing to stop Caroline from going on at length about Elizabeth and her family.
I seriously wish I could have found a video clip of this conversation to share with you, but alas, I've had no luck as of yet (and not for want of at least an hour's time trying). Should that change, I'll come back and post it.