Decker studied in France with Bourdelle, and Despiau and in New York with direct carver Robert Laurent.
Shortly thereafter she began a three-year affair with critic Lewis Mumford, beginning in 1934, but after a mutual parting they both agreed to destroy their correspondence from during this period, fearing that their respective spouses might learn of their relationship.
She later joined a “League Against War, Fascism and Lewis Mumford” with his wife Sophia and another former lover of his, Catherine Bauer.
De Coux carved two reliefs, ""The Oldest Church in the Valley” and Ploughing for the post office in Palmyra, Pennsylvania.
Decker was married twice, from 1934 to 1936 to Duncan Ferguson and to financier Davidson Summers from 1938 until her death in 1979 with whom she had at least one child, Elizabeth Spaulding of Economy, Nova Scotia.