"No," said Darcy, "I have made no such pretension. I have faults enough, but they are not, I hope, of understanding. My temper I dare not vouch for. It is, I believe, too little yielding -- certainly too little for the convenience of the world. I cannot forget the follies and vices of others so soon as I ought, nor their offences against myself. My feelings are not puffed about with every attempt to move them. My temper would perhaps be called resentful. My good opinion once lost is lost for ever."

"That is a failing indeed!" cried Elizabeth. "Implacable resentment is a shade in a character. But you have chosen your fault well. I really cannot laugh at it. You are safe from me." (Chapter 11)

I agree Kathi. I think Darcy could have changed Lizzy opinion before Wickham’s story if he had not been so determined to hide his attraction to her. His actions never showed her his original opinion she overheard at the assembly had changed so she saw his behavior as odd or satirical, looking only to criticize. I think of her behavior to him then as wary. I think her criticism of Darcy’s implacable resentment in Chapter 11 attests to the fact she was open to change herself. I also agree her opinion changed from thinking he was only disagreeable to both disagreeable and dishonorable after Wickham story; you are right it was not a coincidence she tells Darcy it was a month before she understood he was the last man she could ever marry—to me this means she always knew she could not ever connect herself to a dishonorable man. However, her opinion even after Wickham is not implacable although she has to be shown the error of her ways instead of figuring it out for herself she is finally able to reevaluate her opinion of Darcy. I think Darcy’s letter nearly resets her opinion to its status before Wickham’s story. I do think she cannot approve Darcy for his treatment of Jane although she does come to understand his justification more as time goes on and his disagreeableness in company. ;D