Is she or isn't she?

What I find interesting in the first twenty chapters or so of Pride and Prejudice is the seemingly selective analytical skills of the heroine Elizabeth.  On the one hand, she is considered to be extremely intelligent, making her the favorite of her father and the least favorite of her mother.  As a reader I am willing to accept it on nearly all accounts.  she is certainly clever, and is usually an excellent judge of people and their intentions.  This is, however, proven incongruous by her judgment of Mr. Wickham, who is clearly inconsistent in his first stating that it would have to be Mr. Darcy who prevented himself from encountering Wickham, yet in practice it is Wickham who creates false pretense not to attend the ball which Darcy attends.  Elizabeth’s eager willingness to accept Wickham’s explanations without better getting to know his character or gather the opposite side to the story is not consistent with her personality as developed throughout the beginning of the novel.  Several explanations can be provided for this inconsistency.  One cause could be the preconceived bias that she has built up against Darcy through the course of the first ball and their following interactions.  Another possible cause could be that she is falling in love with Wickham, who will undoubtedly prove a scoundrel by the end of the novel.  Either way, it would seem in matters of love Elizabeth is unable to employ her intelligence to her advantage, both in detecting Darcy’s affections for her (which she notices but interprets incorrectly as contempt [how could anyone outside of grammar school fail to see the difference between love and contempt?]) and in trusting Wickham.  Her misunderstandings with these two characters seems to undermine the credibility she accrues through seeing Mr. Collins for the fool he is and Miss Bingley as the conniving bitch that she is.  So what are we to make of Elizabeth?  I she an intelligent woman who is easily influenced by emotion or is she as dense as Mr. Collins with the occasional stroke of luck?  You tell me in the comments.