After leaving high school she became the resident ingenue at the Hal Roach studio, appearing opposite Roach's comedy stars Harold Lloyd, Snub Pollard, and Stan Laurel.

In 1919, Roach formed a company headed by Pollard, with Mosquini as leading lady.

[3] After obtaining a divorce from Harlow in October 1930,[4] Mosquini retired from acting and married an inventor 26 years her senior: Lee de Forest.

[5] In 1967, Mosquini donated her husband's papers and historic prototypes to the Perham Foundation, now held at History San Jose.

In 1968, she became a Novice Class amateur radio operator; her call sign was WB6ZJR.