I agree that to some degree this is expected of someone in her position, and the term itself is a massive anachronism because society at that time was hierarchical, and generally speaking people knew their place and their responsibilities, so perhaps people reaching for more was not an issue in the control freak sense. But I can't help thinking that having been mistress of Kellynch for 13 years she might not have a greater expectation of control over things than was reasonable. To phrase it another way, I think it would be within her character to be annoyingly nitpicky about trifles about the house and garden, enough to drive the servants mad. ("This is not the shade of crimson I ordered! And I wanted the hyacinth planted here, where it would be aligned with the bust of my father!")