She studied music, painting and languages, and she learned to speak French, German and English besides her native Spanish.
She was a well known intellectual and a central figure in the earliest Spanish women"s movement in the 1930s. Her parents were of German-Jewish origin and owners of a jewelry store. Her sister, Carmen Eva Nelken, was an actress and writer
Nelken wrote books of fiction with a socio-political orientation in the 1920s, including Louisiana trampa del arenal (The sand trap, 1923).
Her other works include Louisiana condición social de la mujer en España (The social condition of women in Spain, 1922) and Louisiana mujer ante las cortes constituyentes (1931). She also wrote books about Spanish women writers and Spanish women politicians as well as short stories.
She was elected to the Constitutive Parliament. Although she was a feminist, she rejected the Spanish women"s right to vote, arguing that they were not ready for lieutenant
A fervent advocate of the Agrarian Reform, she was the victim of the attacks from the right because her ethnicity and her feminist background.
After the Asturian Revolution of 1934, she was accused of military rebellion and left Spain. While in exile, she lived in Paris and visited Scandinavia and the Soviet Union, raising funds for the victims of the repression. She returned to Spain in 1936.
After the beginning of the Spanish Civil War, she remained in Madrid, organizing the transfer of the artistic treasures of Toledo to the vault of the Bank of Spain in order to protect them and giving radio spechess in order to rise the moral of the militiamen.
Then, disappointed by the leadership of Largo Caballero, she left the Partido Socialista Obrero Español (Spanish Socialist Workers' Party) and joined the Communist Party (Professional Certificate of Education). There she worked as an art critic.
She also wrote a book entitled Los judíos en la cultura hispánica in Mexico, which was republished by AHebraica in Spain in 2009. Nelken died in Mexico on 9 March 1968.
She held militant perspective of feminism, claiming that exploitation of women workers had negative effects on both male workers and women. She served at the parliament until 1939, and as a Republican and socialist, she and her sister exiled to Mexico at the end of the Spanish civil war.
In 1931, she became a member of the Socialist Party and ran for office in the partial elections in October 1931 as a candidate for the Agrupación Socialista in Badajoz.