] He left Mrs. Norris in charge far too long, until he awoke to the need to take an active role.

Slavery is the analogy, women attached to Sir Thomas are what concerns JA. Mrs. Norris as the plantation manager makes a lot of sense; no real authority but enjoys exerting what she can on behalf of Sir Thomas, just a little more financial independent than the other females, lives in a house on Sir Thomas' estate MP and manages things very badly in his absence.