Hamer published in various journals and magazines, writing on diverse topics including art, literature, music, the economy, education, history, and politics.

[1] Little is known of her early life, but the family moved to Antwerp and Hamer participated in literary circles and women's social reform activities.

[2] Hamer was involved with the Cercle des Dames de la Croix Rouge (Women's Circle of the Red Cross), serving as its general secretary.

[3] Baroness Florence de Laveleye (née Wheeler) served as the inaugural president of the alliance and Hamer was appointed as assistant secretary.

[1][5] Although the organization was officially apolitical, the Alliance Belge pour la Paix par l'Éducation was part of the feminist social reform movement, maintaining that education and women's suffrage were important tools to prevent war.

[7][8] She informed La Fontaine that her organization would lose important ties to other feminist organizations like the Conseil National des Femmes Belges (National Council of Belgian Women) and the Vrouwehvereeniging der Antwerpen (Women's Association of Antwerp), which gave her association access to international journals, publishing, and fundraising networks.

[8] During World War I, Hamer served as a nurse and organized fundraisers to establish an ambulance service and adequate supplies to care for the wounded.

[5] Hamer and Sarton, along with three delegates for the Cercle de Dames et Jeunes Filles Sionistes (Circle of Zionist Ladies and Young Women) persuaded the German authorities to grant them travel documents.

[13][14] As a symbol of the importance of cooperation, the German attendees, led by Anita Augspurg, suggested that all of the Belgian delegates be seated on the rostrum.

[22] In 1925, she and Marguerite Nyssens,[Notes 1] worked to reestablish the Brussels chapter of the Alliance Belge pour la Paix par l'Éducation but without success.

Frequently writing about the relationship of Belgium with Poland and Slavic countries, Hamer joined and became secretary of the organization Comité des amities polonaises (Belgian-Polish Friendship Committee).

[25] Hamer published in various journals and magazines, writing on diverse topics including art, music, the economy, education, history, and juvenile crime.

[1] She published two books, Histoire des littératures slaves (History of Slavic Literature) and Relation de voyage (Account of a Journey) and later collaborated with the journal L'Écho du Soir (The Evening Echo).