I doubt that Jane could feel much superiority as a city girl, after all -- chap 20 --

"The plan was that she should be brought up for educating others; the very few hundred pounds which she inherited from her father making independence impossible. To provide for her otherwise was out of Colonel Campbell's power; for though his income, by pay and appointments, was handsome, his fortune was moderate and must be all his daughter's; but, by giving her an education, he hoped to be supplying the means of respectable subsistance hereafter."

Jane's jealousy towrds the end was the natural jealousy of a woman whose fiance was paying attentions to another woman. Jane got along very well with the Campbells --

"The affection of the whole family, the warm attachment of Miss Campbell in particular, was the more honourable to each party from the circumstance of Jane's decided superiority both in beauty and acquirements. That nature had given it in feature could not be unseen by the young woman, nor could her higher powers of mind be unfelt by the parents. They continued together with unabated regard however, till the marriage of Miss Campbell, who by that chance, that luck which so often defies anticipation in matrimonial affairs, giving attraction to what is moderate rather than to what is superior, engaged the affections of Mr. Dixon, a young man, rich and agreeable, almost as soon as they were acquainted; and was eligibly and happily settled, while Jane Fairfax had yet her bread to earn."