Yes, I would certainly agree that it was Elizabeth's vanity that led her to be so easily deceived by Wickham. When Elizabeth begins to reproach herself after reading Darcy's letter, one of the things she says is that she "prided [herself on her] discernment" and "gratified [her] vanity, in useless or blameable distrust" (Ch. 13, Vol. 2). In other words, Elizabeth believed herself very capable of understanding between right and wrong, and a good person and a bad person. Her vanity is not so much in her physical appearance as it is in her wisdom and her intellect. When Elizabeth met Wickham, she felt flattered because he was easy-going, friendly, handsome, charming, and seemed to be attracted to her. He represented the exact opposite of Darcy who was cold, reserved, proud, and even insulted her. So, yes, it was Elizabeth's vanity that responded so quickly to Wickham, but not only that. Her naivete also led her to be attracted to Wickham, particularly naivete in truly understanding, or discerning character. Elizabeth naively mistook exuberant friendliness for strength of character. Being a friendly person does not equate to being a good and true person. Likewise, with respect to Darcy, she mistook prideful reserve for meanspiritedness and immoral conduct. But as we see with Darcy, being reserved and having pride in who you are does not equate to being a bad person. Hence, both vanity and naivete led Elizabeth to be misguided by Wickham.

In contrast, while Jane seems naively to think too well of people, when it came to understanding Darcy, Jane's ability to discern was actually better than her sisters. Jane's reasoning was purely logical. Jane knew that Bingley was amiable and trustworthy, and therefore would not possibly have a friend who was so very capable of unscrupulous behavior as Wickham claimed Darcy to be. At least in this instance, Jane's natural ability to trust led her in the right direction; she was absolutely correct to believe Bingley's and his sisters' claims that Wickham was untrustworthy (Ch. 18, Vol. 1).