Emmy Thornam first attended drawing classes at the Technical School in Horsens and later studied at Vilhelm Kyhn’s (1819–1903) Drawing School for Women from 1873 to 1875. After beginning her career as a landscape painter, she later shifted her focus to flower painting, which became her livelihood. She trained under O.A. Hermansen (1849–1897) and, in 1894, studied with the flower painter Pierre Bourgogne (1838–1904) in Paris.

As a flower painter, her style evolved over time from a traditional, more decorative approach to a looser technique with greater compositional cohesion. Emmy Thornam exhibited actively throughout her life and supported herself as both an artist and a writer. She authored the memoir Min Søster og jeg (My Sister and I), which provides a nuanced insight into the life of a female artist in the late 19th century.