The passage you are thinking of, I assume, is "Elizabeth could not help observing, as she turned over some music books that lay on the instrument, how frequently Mr. Darcy's eyes were fixed on her. She hardly knew how to suppose that she could be an object of admiration to so great a man; and yet that he should look at her because he disliked her was still more strange. She could only imagine, however, at last, that she drew his notice because there was a something about her more wrong and reprehensible, according to his ideas of right, than in any other person present. The supposition did not pain her. She liked him too little to care for his approbation." (BTW, if you click on "Pop up the novel text" you can get a searchable or browsable version of the novel, whereever you have an internet connection.)