The reason she rejected him was due to the way she perceived his mistreatment of Wickham. She didn't realize just how bad of an egg he was, and how lucky Wickha

The reason she rejected him was due to the way she perceived his mistreatment of Wickham. She didn't realize just how bad of an egg he was, and how lucky Wickham was to have a connection with Darcy. Upon receiving Darcy's letter, where he bares his entire soul and how he went to considerable expense to make things right for Wickham and her sister anyway, she began to see him in a new light. She was already well down the path to falling for him when they toured his estate the first time. Obviously that sealed the deal, but Austen wouldn't be hailed as one of the world's greatest novelists if the plot of her seminal work was that easily reduced to money.