Who is Catharina Vermeer from Girl with a Pearl Earring and what is their importance?

Catharina Verneer is Johannes' wife. She is described as a tiny blonde, who exists in a world of chaos and multiple pregnancies. Catharina has little interest in her husband's work unless it produces income and little interest in her children. She is extremely jealous of Griet's place in her husband's life and outraged when she sees the completed painting, in which, Griet is wearing her earrings.