Jenny af Forselles entered the Imperial Alexander University to study literature in 1896. She finished her BA in 1899 and year later she obtained a Master’s. af Forselles became one of the first female PhDs in Finland in 1904. Her dissertation, A. N. Clewberg-Edelcrantz och omgifning (‘A. N. Clewberg and his environment’, 1903), discussed poet and inventor Abraham Niclas Edelcrantz’s cultural life around the turn of the 1800s.

After graduating af Forselles became a teacher, like many of the educated women of her time. She started as a teacher of Swedish, German and History at the Swedish private girls’ school in Helsinki in 1905 and she continued there until 1937. Her devotion to teaching made her a prominent and respected influential woman, especially among Helsinki’s Swedish-speaking population.

af Forselles continued her academic work for a few more years, translating the writings of Elias Lönnrot into Swedish. As a result, the Society of Swedish Literature in Finland published Elias Lönnrots Svenska skrifter utgifna af Jenny af Forselles (‘Elias Lönnrot’s Swedish writings translated by Jenny af Forselles’) in two parts in 1908 and 1911. af Forselles’ academic work stopped when she entered politics.

af Forselles’ political career began when she entered Parliament as a member of the Swedish People’s Party in 1909. Her academic training and work as a teacher granted her a seat on the Education and Culture Committee in Parliament. Her main goal in her parliamentary work was the reform of social welfare legislation and the support and development of the education system – especially in regards to private schools. af Forselles served as a Member of Parliament until 1917, after which she moved to local politics in the Helsinki City Council and focused on social work as well as the advancement of women.

After the Finnish Civil War, af Forselles actively participated in the founding of the Mannerheim League for Child Welfare in 1920. She was involved in organising clubs and summer camps for underprivileged children, where she spent many summers when she didn't have family obligations. Along with the Helsinki Scouts, she organised a Christmas collection to benefit the city’s poor from 1920–1938.

af Forselles also helped those from the White Side of the Civil War who had been injured. She had a significant role in the founding of the Disabled Civil War Veterans’ Summer Lodge on the Porvoo archipelago and she initiated the establishment of a home for disabled veterans at the Kyyhkylä Manor in 1927.