Answer by taking a quote from the following article:

Lillian Evelyn Moller Gilbreth (May 24, 1878 - January 2, 1972) was an American psychologist, industrial engineer, consultant, and educator who was an early pioneer in applying psychology to time-and-motion studies. She was described in the 1940s as "a genius in the art of living." Gilbreth, one of the first female engineers to earn a Ph.D., is considered to be the first industrial/organizational psychologist.

For more than forty years, Gilbreth's career combined psychology with the study of scientific management and engineering. She also included her perspectives as a wife and mother in her research, writing, and consulting work. Gilbreth became a pioneer in what is now known as Industrial and organizational psychology. She helped industrial engineers recognized the importance of the psychological dimensions of work. In addition, she became the first American engineer ever to create a synthesis of psychology and scientific management. (Gilbreth introduced the concept of using psychology to study management at the Dartmouth College Conference on Scientific Management in 1911.)  In addition to jointly running Gilbreth Incorporated, their business and engineering consulting firm, Lillian and Frank wrote numerous publications as sole authors, as well as co-authoring multiple books and more than fifty papers on a variety of scientific topics. However, in their joint publications Lillian was not always named as a co-author, possibly due to publishers' concerns about a female writer. Althhough her credentials included a doctorate in psychology, she is less frequently credited in their joing publications than her husband, who did not attend college.  The Gilbreths were certain that the revolutionary ideas of Frederick Winslow Taylor would be neither easy to implement nor sufficient; their implementation would require hard work by engineers and psychologists to make them successful. The Gilbreths also believed that scientific management as formulated by Taylor fell short when it came to managing the human element on the shop floor. The Gilbreths helped formulate a constructive critique of Taylorism; this critique had the support of other successful managers.

Did she have any other career highlights?
she became the first American engineer ever to create a synthesis of psychology and scientific management.