Who is Mrs. Arkwright from Oranges Are Not the Only Fruit and what is their importance?

Mrs. Arkwright sells products to control vermin. Her business is flailing, and at one point, she tells Jean that indoor plumbing and central heating have hurt her business. In order to attain the money she needs to set up a new business elsewhere, she plans to burn down the building of her vermin control business and use the insurance money. She swears Jean to secrecy.