The farewell between herself and Mr. Wickham was perfectly friendly; on his side even more. His present pursuit could not make him forget that Elizabeth had been the first to excite and to deserve his attention, the first to listen and to pity, the first to be admired; and in his manner of bidding her adieu, wishing her every enjoyment, reminding her of what she was to expect in Lady Catherine de Bourgh, and trusting their opinion of her -- their opinion of everybody -- would always coincide, there was a solicitude, an interest, which she felt must ever attach her to him with a most sincere regard; and she parted from him convinced that, whether married or single, he must always be her model of the amiable and pleasing. (Chapter 27)

Lizzy and Wickham part on good terms; she is still very taken with him. It seems Wickham lets Lizzy know he is grateful for her belief in his story and he wants her to continue believing in him as she heads into country where at least two parts of his story can be specifically verified—what kind of woman Lady Catherine is and that Darcy is to marry his cousin, Anne de Bourgh. I thought Mr. Wickham’s farewell to Lizzy was suspicious. I do not think when leaving someone it is natural to express good will by hoping to always share the same opinions of third parties. It is not natural unless you are worried that your opinions will somehow be challenged—that is the only reason I can think of to explain why Wickham would remind Lizzy of what to expect in Lady Catherine and trust their opinion of everybody would always coincide. Darcy’s relatives might have a better opinion of him than Wickham does; they might also know particulars of why Darcy did not give Wickham the living and Lizzy may hear something of Miss Darcy who Wickham also spoke ill of.

Lady Catherine was a tall, large woman, with strongly marked features, which might once have been handsome. Her air was not conciliating, nor was her manner of receiving them such as to make her visitors forget their inferior rank. She was not rendered formidable by silence; but whatever she said was spoken in so authoritative a tone as marked her self-importance, and brought Mr. Wickham immediately to Elizabeth's mind; and from the observation of the day altogether, she believed Lady Catherine to be exactly what he had represented. (Chapter 29)

In Kent Lizzy consciously continues to verify Wickham’s story though observation. Wickham’s description of Lady Catherine holds true from Chapter 16:

" I suspect his gratitude misleads him, and that in spite of her being his patroness, she is an arrogant, conceited woman."

“I believe her to be both in a great degree," replied Wickham; "I have not seen her for many years, but I very well remember that I never liked her, and that her manners were dictatorial and insolent. She has the reputation of being remarkably sensible and clever; but I rather believe she derives part of her abilities from her rank and fortune, part from her authoritative manner…" (Chapter 16)

Wickham’s story is again verified by the fact (Chapter 30) that Lady Catherine has destined Darcy to marry her daughter and Lizzy looks forward to seeing how he behaves with Anne. Lizzy then determines in Chapter 31 that Darcy exhibits no symptom of love for his cousin. This does not seem much a discrepancy for Lizzy and Wickham did only say “it is believed that she and her cousin will unite the two estates." It is apparently only believed by Lady Catherine; certainly not by Darcy and I cannot be sure Anne has the same opinion as her mother.

"No," said Colonel Fitzwilliam, "that is an advantage which he must divide with me. I am joined with him in the guardianship of Miss Darcy."

"Are you, indeed? And pray what sort of guardians do you make? Does your charge give you much trouble? Young ladies of her age are sometimes a little difficult to manage, and if she has the true Darcy spirit, she may like to have her own way."

As she spoke she observed him looking at her earnestly; and the manner in which he immediately asked her why she supposed Miss Darcy likely to give them any uneasiness, convinced her that she had somehow or other got pretty near the truth. She directly replied --

"You need not be frightened. I never heard any harm of her; and I dare say she is one of the most tractable creatures in the world. She is a very great favourite with some ladies of my acquaintance… (Chapter 33)

In Chapter 33 Lizzy suggests Miss Darcy gives her guardian’s trouble and believes from Col Fitzwilliam’s reaction that she as got pretty near the truth as she understands it from Wickham in Chapter 16—that the sister is like the brother “very, very proud” and used to having her own way. Wickham’s story is pretty much verified by the things Lizzy learns in Kent and although his farewell to her is very suspicious to me so far to Lizzy his story checks out. ;D