Well, you're in for a happy surprise: Mary Beton has a magical purse. When she reaches in to pay for lunch, she tells us, "There was another ten-shilling note in my purse; I noticed it, because it is a fact that still takes my breath away—the power of my purse to breed ten-shilling notes automatically. I open it and there they are" (2.13).
All right, fine. It's not really a magical purse. It's just a way of talking about Mary Beton's inheritance and the kind of mental freedom she gets from financial security. Now that she's got enough money to live on, she doesn't need to do jobs she doesn't like and she doesn't need to suck up to anyone, especially not to men (2.14). That means she can decide for herself what she likes and dislikes, and she has the time and the comfortable room she needs to write all about it.
Want us to blow your mind a little more? "Purse" is a really old euphemism for (and slightly dirty way of talking about) a woman's genitalia. Mary Beton has a self-sufficient purse: she doesn't need a man to fill it.
You figure that one out.