What is the difference between the role of women in 19th-century society and in Pride and Prejudice by Jane Austen?

Really, there is not much difference at all between the role of upper-class women in the early nineteenth century and the way Austen writes them.  Austen has represented upper-class women as essentially having to make the choice between marrying whichever man happens to propose to them, no matter how stupid or inappropriate a match he might be, and running the risk that no one will ever ask her again and that she could end up alone, a burden on her family. 

Charlotte Lucas, for example, feels that she has few options, and she is anxious -- at twenty-seven years old -- to secure "an establishment" for herself.  She doesn't want to be a burden on her family, and she's rapidly approaching old-maid status.  Therefore, when she gets a proposal from Elizabeth's cousin, the ridiculous Mr. Collins, who literally proposed to Elizabeth fewer than forty eight hours before, she accepts.  She figures she has as much a chance of being happy with him as she does if she remains unmarried, and at least she won't be an embarrassment to her brothers.  Likewise, many real-life women found themselves in a similar predicament.  Austen uses Pride and Prejudice to satirize, in part, the terrible choice that society forces on upper-class women of little fortune: marry whoever they can or risk social humiliation as an old maid.  This struggle was real.