Mamlok was born as Ursula Meyer in Berlin, Germany, into a Jewish family, and studied piano and composition with Professor Gustav Ernest and Emily Weissgerber until her family fled Nazi Germany following the nationwide pogrom in 1938. Due to American immigration quotas, the family moved to Guayaquil, Ecuador. Ursula immigrated alone to New York City in 1940 to attend the Mannes School of Music, which had offered her full scholarship on the basis of one of her compositions. Her parents followed in 1941. She became an American citizen in 1945.