One key quote crystallizes the moment that Elizabeth's prejudice against Darcy forms. After she overhears him saying she is tolerable-looking but not pretty enough to tempt him to dance, she is offended, as any young woman would be. Having heard this insult:
Elizabeth remained with no very cordial feelings toward him.
This is classic Austen understatement. "No very cordial feelings" means she dislikes him intensely and is angry at him.
When Elizabeth is helping to care for the sick Jane at Netherfield, she notices Darcy looking at her. As she has developed the firm idea that he hates her, she can only imagine he is looking at her in a way that is critical of her. She assumes that she displeases him. She thinks:
She liked him too little to care for his approbation.
In other words, she tells herself she doesn't need his approval since she hates him anyway.
When Darcy proposes marriage to her, clueless about how much he is insulting her with his arrogant assumption he is doing her a favor, she says:
(The entire section contains 2 answers and 585 words.)