Rosemary "Hot Mama" Horton was a famous jazz singer before the Great War.
Before the Great War, Rosemary was a famous female jazz singer. She was relatively famous, as many posters advertising her can be found around the Mojave Wasteland and the Sierra Madre casino. At one point, she sang for Johnny Uno's Orchestra, another famous jazz act from that time. Her fate after the bombs dropped is left unknown, but she was most likely killed in the blast.
Rosemary Horton is mentioned only in Fallout: New Vegas.