Tigerlily

I think her marriage was more a matter of wealth than status, though status certainly played a huge part. She's part of that class of women not rich enough to live as single women, but sufficiently rich that her getting a job and working for a living would humiliate her family -- especially considering how well Lady Bertram married. I mentioned this in my comment about a later chapter, but I really think that Mrs. Norris would have been happiest if she could have been the housekeeper of a grand household. The head housekeepers were expected not to marry & have children -- and you're right that Mrs. Norris shows a marked disinterest in being a mother herself -- but were responsible for running the household. In many ways she tries to act as housekeeper for the Bertram estate.

She's a woman ill-fit for her place in society, and poorly suited for making the best of it.