Zarah Ghahramani was a 20-year-old university student from a cultured Persian family when she was locked in Iran's notorious Evin prison for political activity she says amounted to letting her hair show from beneath her head scarf. She recounts her beatings with dignified anger in this vivid, sometimes horrifying memoir, My Life as a Traitor mixing scenes from prison with sensual memories of her life before what her father called the regime of the ''primitives.'' (She now lives in Australia.) Her strength: She doesn't let outrage overtake the striking feminine vitality of her storytelling. A-