Pride and Prejudice Volume 2, Chapter 8
The Collinses and their guests aren't invited to Rosings again until the evening of Easter Sunday because Lady De Bourgh had her nephews to entertain her. At dinner that evening Elizabeth finds herself quite entertained by Colonel Fitzwilliam's conversation while Darcy is stuck with his aunt. When Lady De Bourgh notices that Elizabeth and Colonel Fitzwilliam are having such a great time, she intrudes in their conversation to break up their camaraderie. Darcy had also noticed that Elizabeth was enjoying Colonel Fitzwilliam's company. Soon after Lady De Bourgh's interruption and advice that Elizabeth should practice the piano more so that she would be a decent pianist, Colonel Fitzwilliam convinces her to play for him.
Darcy escapes Lady De Bourgh and comes over to watch Elizabeth play, and she asks him if he has come over to intimidate her. He says that he won't argue with her because he knows that she's just trying to bait him into an argument and give him a hard time. Then, at Colonel Fitzwilliam's request, Elizabeth tells him how Darcy offended all of Hertfordshire by dancing only four dances at the first ball he attended when there were ladies having to sit out because there weren't enough men. Her reference to Darcy's behavior that night makes Darcy feel guilty enough to defend himself because that was the evening when he told Miss Bingley that Elizabeth was not pretty enough for him to ask her to dance. Darcy is embarrassed by his behavior, and he doesn't even know that Elizabeth overheard him say that about her. So Darcy says that he didn't know anyone except Bingley and his sisters and he's not good at introducing himself to strangers and pretending to be interested in their small talk. Elizabeth points out that just as her playing the piano would improve with practice, so would Darcy's people skills. Elizabeth plays the piano until it is time to leave and during that time she notices that Darcy is not really partial to Miss De Bourgh as Wickham said he was.