[1][2] She was forced to leave school in 1905 over her involvement in radical politics and moved to Riga, where she was arrested by the Russia authorities for her involvement in an illegal printing press, and was eventually sent to Siberia, escaping imprisonment in 1906 and attending the Russian Social Democratic Party Congress in London in 1907.

[1] She then settled in the Estonian town of Võnnu where, between 1916 and 1917, she was a director of Severopomoštš [check spelling], and in 1917 she moved was elected a member of the Council of Workers and Soldiers, also editing the newspaper Social Democrat (Sotsiaaldemokraadi toimetus) between 1917 and 1918.

[1] She was a city councillor for Tallinn and Tartu,[2] being among the first women to be a city councillor in Estonia, and joined the Estonian Provincial Assembly on 20 November 1918, replacing Jaan Treial; she was also a member of the Asutav Kogu (Constituent Assembly) between 1919 and 1920, and was elected to the first legislature of the Riigikogu (Estonian parliament), in 1920, serving until the end of the session.

[3] Her work in the Riigikogu included introducing a bill concerning family law, which was not passed but influenced subsequent legislation.

[5] Ostra-Oinas's husband Aleksander was arrested by the Soviet authorities and sent to a prison camp in Siberia, where he died in 1942.