Occupied in observing Mr. Bingley's attentions to her sister, Elizabeth was far from suspecting that she was herself becoming an object of some interest in the eyes of his friend. Mr. Darcy had at first scarcely allowed her to be pretty; he had looked at her without admiration at the ball; and when they next met, he looked at her only to criticise. (Chapter 6)

I think it is a bit harsh to accuse Lizzy of being unable to rethink her view of Darcy when he actually does nothing that can definitely be sited as changing his feelings about her. Why do you ask Lizzy to take such a leap of faith when Darcy abused everyone’s faith in him at the assembly? Everyone treated Darcy like the gentleman he was assumed to be but he failed to return the complement and act in a gentlemanlike manner to those at the assembly.

Darcy made it extremely clear Lizzy did not tickle his fancy and he never counters those sentiments with others of equal ferocity. What does he do at Lucas Lodge or Netherfield which counteracts his behavior or his words at the assembly? Why do you think Lizzy should just forget what he said about her and take his behavior afresh without considering his past actions? It is natural, reasonable and logical to filter what a person does and how they feel about you by what they have said and done in the past.