Erna Nonnenmacher (née Rosenberg) was born into a Jewish family in Berlin, Germany on 12 December 1889. She studied design at the progressive Reimann Schule in Berlin and ceramics in Bunzlau. Afterwards, she was employed by the Rosenthal porcelain factory as a modeller, and at Fraureuth as a sculptor, sharing a studio with her husband and fellow sculptor, Hermann Nonnenmacher. Following the rise of Nazism, the Nonnenmachers fled to England in 1938. They held their first London exhibition at the furniture shop of Gerald Holtom (future inventor of the symbol for the Campaign for Nuclear Disarmament), who then had a shop in Tottenham Court Road. When internment for so-called 'enemy aliens' was introduced in 1940, Erna was briefly interned in Holloway prison, then in Rushen camp on the Isle of Man; men and women were held separately and Herman was interned in Onchan camp. After release, they exhibited with the Artist’s International Association (AIA) and Free German League of Culture (FGLC) in 1941, and at Ben Uri Gallery.
After the war, in 1946, Nonnenmacher was was one of several émigré sculptors invited to exhibit with the Women's International Arts Club (WIAC), where she exhibited four works, predominantly on a maternal theme: Young Mother, Madonna and Child, Kathleene and The Mothers (terracotta). She exhibited sculpture and portraiture in various materials regularly at Ben Uri Gallery, including in a three-person show with Walter Trier and Elsa Fraenkel in 1947, annual shows in 1958 and 1963, and Ben Uri's inaugural shows at new gallery premises in Berners Street (1961) and in Dean Street (1966). She also assisted her husband Hermann in teaching modelling and pottery at Morley College for adult education (1949–70). In 1964, at the age of 75, she was elected an Associate of the Royal Society of British Sculptors.
Erna Nonnenmacher died in London, England in 1980. Her work is represented in the Ben Uri Collection.