When she goes on walks in the countryside near Rosings, Elizabeth keeps running into Darcy by chance. During one meeting, he questions her about Charlotte's happiness and about her own feelings for the neighborhood, Elizabeth suspects that he may actually be trying to set her up with Colonel Fitzwilliam.
Darcy tries to figure out if Elizabeth will accept him and move to Pemberley, which is nearby Rosings. But her prejudice against him leads Elizabeth to an entirely different interpretation.
On another day, Elizabeth meets Colonel Fitzwilliam on a walk. As they talk, he tells her that as a younger son, he has concerns that Darcy does not have: for instance, about having to marry for money. Elizabeth blushes.
Unlike Wickham, Colonel Fitzwilliam is a good man. But just like Wickham, Fitzwilliam must take into account financial concerns when thinking about marriage.
During the same conversation, Colonel Fitzwilliam relates a story about how Darcy intervened before one of his friends made an "imprudent marriage." Elizabeth realizes that Fitzwilliam is unknowingly referencing a story about Bingley and Jane, and is appalled to realize that Darcy ruined Jane's chances with Bingley. Darcy, she thinks, must have selfishly wanted Bingley to marry Georgiana instead.
Predisposed to think of Darcy as prideful, Elizabeth's opinion of him only gets worse when she hears the story. She can't imagine that Darcy may have had legitimate concerns about Jane or the Bennets and sincerely wanted to protect his friend.