Lynn Nottage's Pulitzer Prize-winning account of sexual violation and torture among young women in the Democratic Republic of the Congo is a Kilimanjaro of a play — and it takes a mountain climber of an actress to scale its lofty peaks. Nottage modeled the swaggering character of Mama Nadi, who runs a bar and brothel in a Congo rainforest, after Bertolt Brecht's indomitable Mother Courage. But don't tell Mama that. She is her own life force, beholden to no one. At the Black Rep, she was brought to robust life in a towering performance by Andrea Frye. A commanding presence, Frye strode the Grandel stage with authority and braggadocio. A sense of unpredictable danger suffused her every move. In holding audiences rapt with her charisma, Frye brought a vital life force to a play whose subject matter otherwise might have been too grim to contemplate.