Hesselgren was given the Illis Quorum in 1918, and in 1921 she became one of the five first women to be elected to the Swedish Parliament after women suffrage alongside Nelly Thüring (Social Democrat), Agda Östlund (Social Democrat) Elisabeth Tamm (liberal) and Bertha Wellin (Conservative) in the Lower chamber. Hesselgren was alone in the Upper chamber and thereby became the first woman in the Upper chamber. She was a liberal in 1922–23 and 1937–44 and Independent in 1923–1937.