Kitty returned from Europe to the U.S., where she obtained a Bachelor of Arts degree in botany from the University of Pennsylvania. In 1938 she married Richard Harrison, a physician and medical researcher, and in June 1939 moved with him to Pasadena, California, where he became chief of radiology at a local hospital and she enrolled as a graduate student at the University of California, Los Angeles. She and Oppenheimer created a minor scandal by sleeping together after one of Tolman's parties, and in the summer of 1940 she stayed with Oppenheimer at his ranch in New Mexico. When she became pregnant, Kitty asked Harrison for a divorce and he agreed to it. On November 1, 1940, she obtained a quick divorce in Reno, Nevada, and married Oppenheimer.