After graduating from the University of Minnesota in 1929, Van Riper came to Los Angeles that same year and landed a job writing scripts for a local radio station. While there, an interest in writing historical novels found expression in her creation of the series English Coronets, in which she wrote, directed, and acted. From 1936 until 1944, Van Riper was under contract at MGM as a screenwriter. Eventually, she earned $1,500 a week writing several installments of the studio's popular Andy Hardy series: Judge Hardy's Children (1937), Out West with the Hardys (1938), Andy Hardy Gets Spring Fever (1939), and The Hardys Ride High (1939). In addition to the Hardy films, the talented scenarist also wrote and collaborated on Babes in Arms (1939), The Harvey Girls (1946), and others. For 20 years, however, Van Riper's body had been wracked with spinal arthritis and a sciatic condition of the legs that eventually became unendurable. Forced into semi-retirement by her maladies, the writer tried to end it all with pills on September 14, 1948, but an inhalator squad managed to save her life. On December 31 of that same year, Van Riper's mother found her pajama-clad daughter dead from an overdose of sleeping pills slumped in front of her bed in her home at 1237 Valley View Road in Glendale, California. Authorities listed her death as suicide although the 40 year old had not left a note.
The Kay Van Riper papers are held at the Academy of Motion Picture Arts and Sciences, Margaret Herrick Library.