Okay, I know people during this period were much more formal than we are now in addressing each other. I've been a JA fan for enough years that I long ago got over my surprise at married people calling their spouses Mr. This and Mrs. That, but for siblings to address each other so formally still freaks me out. I can understand Mrs. Norris *referring* to her sister as "Lady Bertram" when speaking to others, but to address her own sister with the honorific just seems absurd to me. For pity's sake, they were brought up together, they surely called each other by their first names while growing up, and on top of everything else, Mrs. N is the older sister. Surely Lady B wouldn't have minded if Mrs. N had addressed her simply as "Maria," at least when they were alone together.