Has Jane learnt somewhat more mistrust of people during the course of the novel?
It takes Elizabeth an awfully long time in chapter 59 to convince Jane that she really does love Darcy.
"You are joking, Lizzy. This cannot be! -- engaged to Mr. Darcy! -- No, no, you shall not deceive me. I know it to be impossible."
"Oh, Lizzy! it cannot be. I know how much you dislike him."
"You know nothing of the matter. That is all to be forgot. ... "
Miss Bennet still looked all amazement. Elizabeth again, and more seriously, assured her of its truth.
"Good Heaven! can it be really so? Yet now I must believe you," cried Jane.
But still Jane doesn't believe her:
"My dear, dear Lizzy, I would -- I do congratulate you; but are you certain -- forgive the question -- are you quite certain that you can be happy with him?
"There can be no doubt of that. It is settled between us already that we are to be the happiest couple in the world....
And Jane is still doubtful:
"Very, very much. Nothing could give either Bingley or myself more delight. But we considered it, we talked of it as impossible. And do you really love him quite well enough? Oh, Lizzy! do anything rather than marry without affection. Are you quite sure that you feel what you ought to do?"
And only finally, after more speeches by Elizabeth does she convince Jane that she does care for Darcy.
This passage just struck me in contrast with how quick Jane is to believe that Caroline Bingley is not trying to separate her and Darcy, and to try to believe that Charlotte feels something like regard and esteem for Mr Collins (chpt 24).
Jane has learnt somewhat more caution in her judgment of people during the course of the novel, she has had her own growth, perhaps not as dramatic as Elizabeth's, but real nonetheless. Though I do love this touch:
Miss Bingley's congratulations to her brother on his approaching marriage were all that was affectionate and insincere. She wrote even to Jane on the occasion, to express her delight, and repeat all her former professions of regard. Jane was not deceived, but she was affected, and, though feeling no reliance on her, could not help writing her a much kinder answer than she knew was deserved. (chpt 60).