James Brown said it best: "It's a Man's Man's Man's World. Why? Because men have all the power. Or do they? You could argue that A Room of One's Own is all about power: men's power over women, women's power over men and over themselves, and even artistic power. Woolf carefully traces the effects of power on the minds of both men and women, showing that the power that men have has to come from believing that women are inferior. For Woolf, too, the power of authority is the power to interrupt. In order for women to write well and express their thoughts completely, of course, they can't be interrupted. They have to take back the power.
If you can write about someone else, you have power over that person.
Mary Beton's inheritance makes it so she doesn't have to be a magical "looking glass" that enlarges men.