The next evening, Elizabeth is amused at the conversation between Mr. Darcy and Miss Bingley. Miss Bingley throws a steady stream of compliments and requests at Mr. Darcy, who replies with his own dry sense of humor or ignores her.
Elizabeth observes that the banter between Mr. Bingley and Mr. Darcy proves that Mr. Darcy notices the reasons why people behave the way they do.
Mr. Bingley, Mr. Darcy, and Elizabeth discuss the merits of changing your mind because a friend persuades you to. Mr. Darcy says that you're a fool if the only reason you yield to a friend's opinion is because they have that opinion. In other words, don't act just to please somebody else. Elizabeth, alternatively, argues that a trusted friend's opinion should be enough to sway you.
Not to hit you over the head with it, but this discussion is foreshadowing later parts of the plot, like when Mr. Bingley will be persuaded by Mr. Darcy that Jane doesn't care about him, even though his own heart says otherwise.
Elizabeth notices how frequently Mr. Darcy looks at her and she wonders why. She assumes he can't possibly be interested in her and decides that the only reason he keeps looking at her is to find things that are wrong about her. When he looks, she thinks, he looks to judge.
The group listens to Mr. Bingley's sisters play the piano and Mr. Darcy asks Elizabeth if she would like to dance. She ignores him and he repeats his request. She responds that she would rather not give him the pleasure of mocking her, so no, she will not dance with him.
Miss Bingley gets jealous, realizing that Mr. Darcy is beginning to get really interested in Elizabeth.
As for Mr. Darcy, he is "bewitched" but thankful that Elizabeth's social status is so beneath him that he can't possibly be tempted into any kind of serious relationship.