“Something like this only happens once in a lifetime,” someone says with heavy dramatic irony towards the end of White Girl. Thank heavens, because if we all lived as fast as the protagonist here no one would survive long enough to reproduce. First-feature-maker Elizabeth Wood’s cocaine-dusted, semen-soaked provocation takes an unapologetically pitiless look at one privileged young woman’s walk through the hot coals of crime, class and desperation. Seductive and repellent by turns, it’s a title that will provoke fierce love-or-hate reactions, but there’s no question it augurs the arrival of a powerful, audacious new directorial talent. Meanwhile, it will irrevocably supercharge the career of Morgan Saylor, best known previously as the petulant teen daughter from Homeland, who is outstanding here as the title character.