I think there is an element of subjectivity to this question, especially given the more satirical elements within Pride and Prejudice and the way in which Austen portrays the society in which she herself resided. You need only read the histrionic excesses of Mrs. Bennet (coupled with the often sardonic commentary of her husband) or the conceited mediocrity of a Mary Bennet to note that there is often a very biting quality to Austen's writing. But this raises one of the great challenges of satire, because in poking fun of these stereotypes and archetypes, Austen must also place them center-stage within the novel. Thus, there is a degree of ambiguity to this question as to whether such characters do more more to undermine or reinforce the stereotypes in question.
At the same time, I do think it is worth remarking that Elizabeth Bennet, taken in and of her own terms, is a remarkably self-possessed woman possessed of wit, intelligence, and a strong sense of will (to go along with very clear character flaws reflected in her interactions with the other characters around her). Indeed, even as she does eventually marry Darcy, you should remember just how much of their interactions within the novel are defined by hostility on her part, and moreover, remember that her initial response to his marriage proposal is to reject him (which, seen within the often mercenary context of nineteenth century marriage negotiations is a remarkably radical move for a woman in Elizabeth's position). Furthermore, however, it might also be worth comparing Elizabeth with her friend Charlotte Lucas, who self-consciously embodies that same mercenary streak that Elizabeth ultimately rejects, but in a way that seems motivated by a desire to maintain some measure of control over her own fate (intent on seizing what measure of happiness and security she can find). It is because of these characters, and the very real sense of personality that Austen imbues them with, that I think this story moves beyond the realm of stereotype to provide a very vivid, if often bitingly satirical, picture of life.