Rygier was a follower of Arturo Labriola and of the socialist avant-garde in Italy. In 1907 she became editor of the newspaper Lotta di classe, a socialist revolutionary publication. With Filippo Corridoni, she also founded the anti-militarist broadsheet Rompete le file. She voiced the opinion that women should oppose militarism, as they gave birth to the soldiers killed in war on behalf of the state.
A World War I interventionist in 1914, she became an editor at the newspaper founded by Benito Mussolini, Il Popolo d'Italia. The socialist daily founded by Mussolini was devoted to supporting the campaign for intervention by Italy in the War. As a syndicalist and union supporter, she was jailed for a period in 1914. Her status as a political prisoner fighting for syndicalism became known to Italian-American syndicalists during the period. Anarchist Leda Rafanelli urged Italian workers to follow the example of Rygier.
After a brief nationalist period, she fled to France in 1926, by then in open opposition to Fascism. While in France, Rygier published a pamphlet highly critical of Mussolini. The 16-page pamphlet was originally written in French. The pamphlet was translated and published worldwide in 1928, revealing how Rygier became disillusioned with Mussolini, accusing him of being an informer, engaging in blackmail, and of using tactics harmful to Italy's national interests yet beneficial to its future allies. She further accused Mussolini of political opportunism to further his personal interests, such as taking a lucrative newspaper job that required switching political orientation:
...I have already explained, in the French press, that being a fervent interventionist myself, I had been, to some extent, responsible for the "conversion" of Mussolini due to the advice I gave the French Ambassador at the Quirinal, M. Barrère, to start a daily socialist paper devoted to the interests of the Allies at Milan, an important industrial center and therefore proletariat. My suggestion was well received by France and carried out to the letter with the exception, however, of the selection of the future manager of the paper.
Not having then the least idea that Mussolini was for sale I had not suggested his name to M. Barrère. I had suggested the name of a well-known syndicalist already favorable to the cause of intervention. [...] when I learned that France had succeeded in hiring [...] the flag-bearer of neutrality, I conceived a real admiration for that French diplomacy which had realized that powerful trick of discovering Mussolini, or rather of discovering an impetuous interventionist under the mask of an "absolute neutral".
Little is known of Rygier's activities after the publication of her anti-Fascist pamphlet in France and the end of World War II. She returned to Italy after the end of World War II. In 1946, she wrote a polemic book on the exiled anti-Fascists (Rivelazioni sul fuoruscitismo italiano in Francia, Rome, 1946). She eventually became a supporter of the monarchy of Italy. She died in Rome in 1953.
- Whitaker, Stephen B. (2002). The anarchist-individualist origins of Italian fascism. Peter Lang. p. 61. ISBN 9780820457178.
- Topp, Michael Miller (2001). Those Without a Country: The Political Culture of Italian American Syndicalists. University of Minnesota Press. p. 107. ISBN 9780816636495.
- American Co Mason Official Bulletin of the American Federation of Human Rights 1928. American Federation of Human Rights, Larkspur, Colorado, 1928; reprinted by Kessinger Publishing. 2003. p. 189. ISBN 9780766166820.
- Whitaker, Stephen B. (2002). The anarchist-individualist origins of Italian fascism. Peter Lang. p. 177. ISBN 9780820457178.
- Sulla soglia di un'epoca. La nostra Patria, Rome, 1915.
- Rivelazioni sul fuoruscitismo italiano in Francia, Rome, 1946.