It is certain that Caroline Bingley and Elizabeth Bennet are used as foils in this novel. Both, after all, find themselves competing for the affections of Mr. Darcy. It is clear that Caroline Bingley feels threatened by Elizabeth Bennet and that she uses every means at her disposal to try and attack her character and standing with Darcy. Note how the author introduces Caroline Bingley and her sister in Chapter Four of the novel:

They were in fact very find ladies; not deficient in good humour when they were pleased, nor in the power of being agreeable where they chose it; but proud and conceited. They were rather handsome, had been educated in one of the first private seminaries in town, had a fortune of twenty thousand pounds, were in the habit of spending more than they ought, and of associating with people of rank; and were therefore in every respect entitled to think well of themselves, and meanly of others.

At every stage in the novel, when Elizabeth and Caroline are together, it is clear that this level of pride comes through in what Caroline Bingley says, and how she behaves. For an example, consider her behaviour towards Elizabeth when she stays at Netherfield with them during Jane's illness. Caroline Bingley is another character who is an example of pride and its faults. The main differences between Caroline Bingley and Elizabeth are therefore the social standing of Caroline Bingley and her pride, which causes her to act in ways that Elizabeth finds superficial and hypocritical.