Who is Mary Kracha from Out of This Furnace and what is their importance?

Mary Kracha is George and Elena's daughter. She is born at the White Haven camp. When she turns fifteen, Mary goes to work for a wealthy family, where she stays until her marriage to Mike Dobrejcak. The couple has four children. Mary supports the children after the death of her husband, but after being diagnosed with consumption, she is sent to a sanitarium. Mary dies in the sanitarium after a little more than a year.