Dettweiler was born to Helen (nee Berens) and William E. Dettweiler, a restaurant and bakery owner, on December 5, 1914, in Washington, D.C. She had two younger brothers, and all three Dettweiler children played sports, with Helen playing tennis, football, baseball, and softball.[2] Her brother Billy, who qualified for the National Amateur Golf Championship at age 14, got her into golf when he bet her that she could not hit a golf ball four consecutive times, and she lost.[3] Within two years of beginning to play golf, she began to win amateur championships.[2] After graduating from Trinity College, Dettweiler began traveling to play in amateur golf tournaments.[2]
Dettweiler continued to play golf during the broadcasting tour.[6] She won the District of Columbia, Maryland, and Mid Atlantic championships.[7] In 1939, Dettweiler turned professional. She won the 1939 Women's Western Open,[3] and finished in second in the 1940 Titleholders Championship.[8]
Dettweiler co-founded the Women's Professional Golf Association (WPGA) in the 1940s, and was elected as its second president. After the WPGA folded,[2] she was one of 13 founders of the Ladies Professional Golf Association (LPGA) in 1950.[11][12] In 1952, she joined the staff of the Thunderbird Country Club.[13] She also taught at a golf course in Neskowin, Oregon,[14] and organized an invitational tournament there.[15]
Dettweiler remained on the LPGA Tour until the 1960s. After her retirement, she opened a clothing store in Palm Springs, California. Dettweiler died from cancer on November 13, 1990, in Palm Springs.[9]