I agree with post #1, that Mrs. Bennet was operating under the socially accepted norms of the time period, but at the same time, she does it so poorly that her actions come off crude and offensive. Her behavior at Bingley's ball was one of the examples that Darcy felt compelled to relate to Bingley in terms of Jane's low connections and unsuitability.
Mrs. Bennet is worried about her daughters' futures. She has a house full of daughters and when Mr. Bennett is no longer around, there will be no one to care for the daughters. Mrs. Bennet is a concerned mother. One reason Charlotte accepts Mr. Collins proposal is out of a need for someone to take care of her. In Victorian society, it was a concern as to who would take care of one, especially being a woman. Mrs. Bennet is only acting out of concern for her daughters' well being as well as their futures.
In Victorian society, it was generally accepted that moving up in society was accomplished by marrying into a better family, or at least a family of the same social status. Most of Austen’s books center on this theme. To modern societies, this seems strange or even morally repulsive. However, it was the norm. So if we judge Mrs. Bennett, remember we are judging her by modern standards.
I can't think of a way in which Mrs. Bennett goes beyond her rights, so I would have to say yes. Here behavior is not always appropriate, but it is within her rights to act foolishly. She often embarrses her older daughters by her behavior. Again, this is within her rights to do. During this time period, most of her behavior would be typical of a mother. Most mothers attempted to get their daughter into beneficial marriages. Mrs. Bennett is no different. For instance, she denies Jane the carriage for her dinner with Caroline Bingley in the hopes that she will be forced to spend the night. We might not agree with her choice but she certainly had the right to do it. The same could be said for her inappropriate remarks about an advantageous marriage. While it was foolish and embarrassing for her to make these remarks at a party, she certainly had the right to say whatever she wished.