Despite the fact that Jacobs fulfilled all the necessary conditions for enfranchisement, she was not send a ballot like everyone else. When in 1883 her name was not on the just published new voter register, she decided to send a letter to the mayor and councillors of Amsterdam. Her request was refused, because it was the 'spirit' of the law not to extend suffrage to women. A result of this decision, and because of the Supreme Court' rejection of her appeal, the adjective 'male' was added before 'Dutch citizen' whenever enfranchisement was mentioned.
Jacobs also worked for the International Woman Suffrage Alliance (IWSA). Among other things she made two trips with Carrie Chapman Catt to help women in their fight for women suffrage. In September 1906 they travelled to Austria-Hungary and from June 1911 till November 1912 through Africa and Asia.