“She Came to Stay” is a novel written by French author Simone de Beauvoir, an existentialist philosopher, political activist and feminist. The novel revolves around Françoise, whose open relationship with her partner Pierre becomes strained when they form a ménage à trois with her younger friend Xaviere. The moody young woman pries her way between Françoise and Pierre, playing up to each one and deviously pulling them apart, until the only way out of the triangle is destruction.