When Emil Selenka became severely ill during their stay in the Dutch East Indies and had to return to Germany, she continued the work, spending some months exploring the jungles of Borneo to study apes.

Back in Germany the couple wrote a report on their journeys titled Sonnige Welten: Ostasiatische Reiseskizzen ("Sunny Worlds: East Asian Travel Sketches").

She befriended the feminists Anita Augspurg and Lida Gustava Heymann and became involved in the German feminist-pacifist movement, that associated domestic violence against women with the tendency in countries to go to war.

[5] Together with Augspurg, who was Germany's first female professional lawyer, Selenka campaigned for women's suffrage and legal gender equality in the German empire.

She became a member of the Verband fortschrittlicher Frauenvereine (VfFV), Germany's feminist organization that was considered radical at the time.

After a dispute with Augspurg and Heymann she left the VfFV and joined the rival Bund für Mutterschutz und Sexualreform (BfMS), which was founded by her friend Helene Stöcker.

In 1915 she participated in an international peace conference at The Hague, initiated by czar Nicholas II in an effort to stop the First World War.