Who is Helen Rivers from I Know What You Did Last Summer and what is their importance?

Helen is described as a beautiful, selfish young woman. She is dating Barry, but she doesn't have a clue that he is just using her. Helen was Barry's biggest supporter of keeping the pact. She later befriends Collie when he moves into the Four Seasons apartment complex where she lives. Helen receives the second cryptic message: a picture of a boy on a bike taped to her apartment door.