Moldenhauer's father served in the United States Army. She was born in Omaha, Nebraska, and attended Benson High School in Omaha. She graduated in 1949 from the Iowa State College, with a degree in physics,^[1] hoping to go on to a research career in physics was but blocked from that goal because there were few places for women in physics at the time.^[2]

After graduating from Iowa State, Moldenhauer became a high school mathematics teacher in Omaha, and two years later became a student again at the University of Minnesota. She completed a master's degree in mathematics at Minnesota in 1952, and started work as an electrical engineer at General Electric.^[1] Her job there involved the development of fire-control systems for military aircraft. However, bored with her work, she soon returned to high school teaching.^[2] In 1955 she became a high school teacher in Schenectady, New York, where she had been working for General Electric, and in 1956 she moved to Davis Senior High School in Davis, California.^[1]

After 50 years as a teacher in Davis, Moldenhauer retired in 2006.^[2]

Moldenhauer won the Edyth May Sliffe Award for Distinguished High School Mathematics Teaching of the Mathematical Association of America twice, in 1990 and 2001.^[3] She was also a winner of Stanford University's Frederick Emmons Terman Engineering Award, given annually by the graduating engineering students at Stanford to a distinguished high school teacher. She was a two-time winner of Harvey Mudd College's Distinguished Teaching Award.^[1] Unusually for a high school mathematics teacher, Moldenhauer has an Erdős number of 2, from her collaboration with mathematician Sherman K. Stein and mechanical engineer Anthony S. Wexler on "Trigonometry and a Wood Bowl".^[4][5]