[4] Her early work, influenced by Symbolism, Art Nouveau, and the Decadent movement, was exhibited in Brussels and Paris in 1912 and 1913.

For several years Mammen struggled to make ends meet, taking any work she could find, and spending time with people from different class backgrounds.

[7] In time Mammen was able to find work as a commercial artist, producing fashion plates, movie posters, and caricatures for satirical journals such as Simplicissimus, Ulk,[5] and Jugend.

These women subjects often included haughty socialites, fashionable middle-class shop girls, street singers, and prostitutes.

[12] Over the next two years, at Gurlitt's suggestion, she created a series of eight lithographs illustrating Les Chansons de Bilitis, a collection of lesbian love poems by Pierre Louÿs.

[12] In 1933, following Mammen's inclusion in an exhibition of female artists in Berlin, the Nazi authorities denounced her motifs and subjects as "Jewish", and banned her lithographs for Les Chansons de Bilitis.

[12] The Nazis also opposed her blatant disregard for 'appropriate' female submissiveness in the expressions of her subjects as well as the lesbian imagery found in many of her works.

[14] In the 1940s, in a show of solidarity, Mammen began experimenting with Cubism and expressionism, a risky move given the Nazis' condemnation of abstract art as "degenerate".

Her style during this time was characterized by "a simplified, elegant line with a wash of color added later [which] made her popular among high-circulation magazines and journals".

[17] During this time, she was a part of the New Objectivity movement, in which artists attempted to reconcile with a post-WWI Germany by looking at societal issues with "meticulous detail and violent satire".

[18] Under the Nazi regime, she experimented in secret with Cubism and Expressionism to rebel against the government's banning of "degenerate" art.

[16] In 2010 the Des Moines Art Center exhibited 13 watercolor paintings done by Mammen which were inspired by Berlin in the Weimar era.