You are welcome, of course, to jump into the conversation whenever you like!

I think what she saw at Pemberley and heard from Mrs. Reynolds began to change Lizzy's opinion of Darcy, and certainly the change that the letter brought about opened Lizzy to that information, as well as a general change. (Though tangentially, I think that too much weight can be given to evidence that a person is loving and responsible to those within their own circle. Without getting too far off the subject, history teaches us that some poeple who have committed terrible atrocities have shown those characteristics.)

However, I don't believe Lizzy ever would have fallen in love with a man, much less married him, if he believed it was a degredation to be married to her. What Lizzy heard from Mrs. Reynolds and saw at Pemberley did convince her that she had misjudged him to some extent ("[What Mrs. Reynolds said about never having heard a cross word from Darcy] was praise, of all others most extraordinary, most opposite to her ideas. That he was not a good-tempered man had been her firmest opinion"), but it doesn't change the fact that Darcy, as he had told her in the proposal, thought she was inferior and it was a degredation to marry her. It was the change in Darcy that Lizzy saw that really made the difference, and without it, I don't think she ever would have really regretted her refusal.

The second day at Pemberley, Lizzy continues to observe this change, and notices that, if not permanent, it has at least lasted for one day: "whenever [Lizzy] did catch a glimpse [of Darcy], she saw an expression of general complaisance, and in all that he said she heard an accent so far removed from hauteur or disdain of his companions, as convinced her that the improvement of manners which she had yesterday witnessed, however temporary its existence might prove, had at least outlived one day. When she saw him thus seeking the acquaintance and courting the good opinion of people with whom any intercourse a few months ago would have been a disgrace -- when she saw him thus civil, not only to herself, but to the very relations whom he had openly disdained, and recollected their last lively scene in Hunsford Parsonage -- the difference, the change was so great, and struck so forcibly on her mind, that she could hardly restrain her astonishment from being visible. Never, even in the company of his dear friends at Netherfield, or his dignified relations at Rosings, had she seen him so desirous to please, so free from self-consequence or unbending reserve, as now, when no importance could result from the success of his endeavours, and when even the acquaintance of those to whom his attentions were addressed would draw down the ridicule and censure of the ladies both of Netherfield and Rosings."