She wrote five melodramas for Theda Bara during the 1910s popularity of vamp films. She also wrote for Bara's Fox rival, Valeska Suratt. Murillo served as screenwriter for Fox Film from 1916 to 1917, then joining Norma Talmadge Productions in 1919. She returned to the UK in 1923 to work for Stoll Film Studios. She wrote the script for the hit French sound film "Accusée, levez-vous!" (1930). In 1936, she formed the company Opticolor to market in Britain a French motion picture colour system, Francita, developed by her husband, Maurice Velle, son of French film pioneer Gaston Velle, but the business failed after a disastrous demonstration of the system. She later worked for J. Arthur Rank, 1st Baron Rank's Religious Films Ltd.