Mr Darcy noticed that Mr. Bingley was in love with her, but he did not want him to marry her because her family is not rich, and have no connections. He also claims that part of it was because he thought Jane did not show admiration for Mr. Bingley, and assumed she did not have feelings for him.
Darcy's friend who tells Elizabeth that Darcy has separated Bingley from Jane is Mr. Bingley's sister, Caroline. She reveals this information to Elizabeth out of jealousy towards Jane and to further her own interests in marrying Darcy herself.
Elizabeth does not want to hurt Jane's feelings or make her angry. Half of Darcy's letter was about the separation of Jane and Bingley, and Elizabeth did not want to bring it up. Darcy's actions were quite unfair, because he acted without finding the facts. Darcy helped separate Jane and Bingley because he thought Bingley would fall in love only to have his feelings hurt. Darcy thought Jane had no feelings for Bingley, when, in fact, Jane was in love with Bingley. If Elizabeth told her this, it would have given her heartache.
Elizabeth learns about Darcy's role in influencing Bingley by reading a letter Darcy writes to her. In the letter, Darcy reveals that he convinced Bingley to distance himself from Jane Bennet because he believed Jane did not truly love Bingley. This revelation opens Elizabeth's eyes to Darcy's true character and motivations.
Darcy's claim was that he separated them because he saw Bingley had a partiality for Jane unlike any Darcy had seen in him before but he did not detect in her any symptom of peculiar regard. Interpreted a bit for the modern person, this means that he was afraid Jane really did not love Bingley, and wanted to separate the two before Bingley was so deeply in love that he would be hurt. Marrying a woman who really did not care about him would certainly have been worse than unrequited love, but either was to be avoided. Following this assertion, Darcy talked of the family's want of connection, the situation of Mrs. Bennet's family, the want of propriety betrayed by both parents and all three of the younger sisters. He asserted that any connection with such a family would have been most unhappy.
Mainly the Bingley sisters, but also Mr. Darcy.
Elizabeth learned about Darcy's role in separating Charles Bingley from Jane Bennet through a conversation with Mr. Darcy himself during a heated exchange at Rosings Park. Darcy admitted to intervening to protect his friend from what he perceived as an unsuitable match, revealing his involvement in the situation.
Colonel Fitzwilliam provides Elizabeth with several important pieces of information that confuse her understanding of Mr. Darcy. Before meeting with Colonel Fitzwilliam, Elizabeth held the prejudice that Mr. Darcy had no concern for others. Colonel Fitzwilliam speaks highly of Mr. Darcy and commends his dedication to his sister. Elizabeth begins to reconsider her feelings of Mr. Darcy after her friendly chats with Colonel Fitzwilliam. However, eventually Colonel Fitzwilliam casually mentions that Mr. Darcy recently helped save a friend from a relationship he should not enter. Eizabeth immediately realizes that Mr. Darcy interfered with Jane and Mr. Bingley's relationship. Elizabeth becomes incredibly offended by Mr. Darcy's actions and no longer wants to have any interaction with him after learning this information from Colonel Fitzwilliam.
Mr. Bingley returns to Jane because he still has feelings for her and realizes he made a mistake in letting her go. Additionally, his friend Mr. Darcy plays a role in encouraging the reunion between Mr. Bingley and Jane.
Caroline Bingley is the sister of Charles Bingley, Darcy's best friend, and the eventual husband of Jane Bennet. Caroline is hoping to marry Darcy herself, and to have her brother marry Darcy's sister, so she is quite set against Jane and Elizabeth Bennet. She goes out of her way to belittle Elizabeth in front of Darcy, without realizing that she is making herself ridiculous to him every time she talks about it.
Darcy.
Caroline Bingley did not want her brother Charles Bingley to marry Jane Bennet. There were at least two reasons for this. First, the Bingley sisters wanted to elevate their family, which had made its money in trade, to what they regarded as a higher social status, landed gentry. A marriage between Bingley and Jane Bennet would have been to landed gentry, but of a low sort that was intermarried with merchants and attorneys, just the sorts of people they wanted to avoid. Second, she rightly guessed that Darcy was strongly attracted to Elizabeth Bennet, and wanted to keep them separated. A marriage between Bingley and Jane would have tended to put them together more often because Darcy was Bingley's closest friend and Elizabeth was Jane's sister. Caroline Bingley wanted Darcy for herself.
Miss Bingley wants her brother Charles to marry Georgiana Darcy, the younger sister of Mr. Darcy, in Jane Austen's "Pride and Prejudice." She believes that this match would bring wealth and status to their family.