What two elements does Anderson contrast within the poem “triptych” (210) and for what purpose?

In the poem called “triptych,” (210) Anderson depicts “a girl at a private school” (210) who was raped at a party by two boys she had considered to be her friends. She then goes on to tell the story of the two boys’ lives, which had only minor interruptions before leading them to college and degrees and careers and families. The victim, however, is depicted as having struggled with drug addiction for years before finally getting clean and making progress toward her education. Once in community college, however, the young woman’s rape-related PTSD became too much for her to deal with and she dropped out of school. The rapists, meanwhile, were allowed to carry on with their lives as if nothing had happened.