Hays was born in 1920 in Buffalo, New York. Following graduation from high school, she enrolled at Allentown General Hospital School of Nursing, from which she graduated in 1941, having obtained a diploma in nursing. She then joined the Army Nurse Corps in early 1942, and was sent to the China Burma India Theater.
Stationed in India for the duration of World War II, she was on leave in the United States when the war ended. Remaining with the Corps, she saw service during the Korean War. A succession of academic posts followed including a stint at Walter Reed Hospital, and she also earned a Master in Science in Nursing degree. She was promoted on June 11, 1970, after being appointed by President Richard Nixon on May 15, of that year. She was chief of the Army Nurse Corps from September 1, 1967 until her retirement on August 31, 1971.