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

George meets Zuska on the docks at Bremen when they are on their way to America. Zuska is married to John Mihula, and the couple is traveling to Pittsburgh where they will stay with Zuska's sister. After John's death, Zuska accidently runs into George at his butcher shop, and the couple begins an affair. George's wife later passes away, and the couple marries. Their marriage, however, will not be an example of "happily ever after", as Zuska will leave George on account of his abusiveness.