Sleeth was born in Evanston, Illinois. In 1934, she began to study the piano at the early age of four. In 1952, she earned a BA in music theory at Wellesley College in Massachusetts. She married the Rev. Dr. Ronald E. Sleeth, a professor of Homiletics.

The anthem “Hymn of Promise” was composed in early 1985, and dedicated simply to Dr. Sleeth, “To Ron,” who was diagnosed with cancer and died weeks after its premiere. Soon after the anthem was published, it became a hymn under two different names: “In the Bulb There is a Flower,” is sung widely in the United Church of Canada. It appears as hymn #703 in the United Church of Canada hymnal, Voices United, as hymn #433 in The New Century Hymnal produced by the United Church of Christ in the US, and as hymn #707 under the title “Hymn of Promise” in The United Methodist Hymnal. It was translated into German by Lothar Pöll in 1999 and is included in the Gesangbuch der Evangelisch-methodistischen Kirche.

Sleeth received an honorary doctorate from West Virginia Wesleyan College in 1989 and from Nebraska Wesleyan University in 1990. An organist, she wrote over 180 highly successful selections for church and school. One of Sleeth’s best-known anthems for choir is entitled “Joy in the Morning” and was written for the West Virginia Wesleyan College concert chorale on the occasion of her husband’s inauguration as president of the college in 1977.

Sleeth died of cancer in Denver, Colorado in 1992, aged 61. She was a member of the Highland Park United Methodist Church in Dallas, Texas.