Who is Sister Rita from The Dead and the Gone and what is their importance?

Sister Rita is one of the nuns, who helps the girls of Holy Angels care for a garden in Central Park. The garden is designed to give the girls a chance to work for their lunches, in addition to helping themselves provide food for their families. In the end, it is Sister Rita who helps Julie and Alex escape from New York. Sister Rita is described as a loving woman, who does whatever she can to help thise in need.