Who is Marion Kleinmeitz from Requiem for a Dream: A Novel and what is their importance?

Marion Kleinmeitz is Harry's girlfriend. She comes from a wealthy family that she resents for their wealth. Their upper class status has offered Marion a great education and opportunities to travel and see the world and indulge in Art and culture. Marion overlooks that because of the expectations the family has put on her and she feels pressure to meet. She hides from herself and judges the rest of the world constantly. Marion ends up so strung out that she starts prostituting for drugs.