Discuss the relationship between Mrs. Bennet and her children in Pride and Prejudice.

Like any respectable matriarch of the time, Mrs. Bennet is keen to ensure that her daughters are married off as soon as possible to a "single man in possession of a good fortune." Her relationship to them, then, is largely determined by the social mores of Regency England rather than any innate maternal affection she may harbor toward them.
This is illustrated most clearly in Mrs. Bennet's relationship with Elizabeth, her second-oldest child. Elizabeth's mother does not see her as much of a catch, especially in comparison with the charming, pretty Jane or the vivacious, fun-loving Lydia. It is up to Mr. Bennet to remind us that his favorite daughter is incredibly witty and intelligent. He is clearly much less interested in social niceties than his wife, which probably accounts for the fact that Elizabeth is his favorite daughter.
There is little sense throughout Pride And Prejudice that Mrs. Bennet values any of her daughters for their own sake. She simply sees them as a means for the Bennets to ascend the social ladder and attain greater respectability. It is instructive that when Lydia elopes with Wickham, Mrs. Bennet's primary concern is not for her daughter's safety, but for the damage that the elopement will cause to her good name and that of the whole Bennet family.
For Mrs. Bennet, marriage has nothing to do with love or affection; it is related purely to considerations of financial security and social status. In this regard, she is similar to the predominant value system of her time, one not fully shared either by her husband or Elizabeth.