Lambertsen was born in 1916 in Fanwood, New Jersey. She had two brothers. Lambertsen began her career in nursing in the 1930s, working as a bedside nurse while studying at Overlook Hospital. She graduated from the hospital in 1938. Lambertsen was named the school's director of its nursing department five years later, and became its acting director in 1946. She earned a bachelor of science degree in 1949, later a bachelor's in the following year, and became a Doctor of Education in 1957 from Teachers College, Columbia University. Her dissertation brought forward an idea of team nursing called Nursing Team Organization and Functioning. It was published as a book by Teachers College Press in 1953. The result led to Lambertsen leading a dissertation project at Francis Delafield Hospital which attracted many hospital administrators from across the United States who wanted to pursue the reorganization of their staff.
