Kaxilda Hernaez was born in Fraisoro, a house in Zizurkil that sheltered unmarried mothers and orphans. She spent her childhood there until she moved to the Egia neighborhood in Donostia. Her life was marked by her involvement in the anarchist movement and her strong advocacy for women's rights and freedom.

Due to her activism, in 1934 she was arrested carrying explosives and anarchist propaganda, and was sentenced to 29 years in prison. She was incarcerated in the Fort of Guadalupe and later in Alcalá de Henares, until her release after the February 1936 elections.

When the Civil War broke out, she participated alongside Félix Likiniano's group in the defense of Peñas de Aia and the San Marcial mountains. After the fall of Irún, she crossed into Lapurdi and from there to Catalonia to join the Aragon front. Once women were withdrawn from combat fronts, she spent the following months sewing clothes for militiamen in a workshop in Barcelona. After the defeat in the 1936 war, she was interned in the Saint-Cyprien concentration camp, and upon release, she returned to Bayonne. She collaborated with the resistance when the Nazis occupied France.

After a stay in Paris, in 1943 she returned to live in Biarritz, Lapurdi, where she resided until her death in 1992. In the Egia neighborhood of Donostia, she is highly esteemed, and residents have repeatedly asked the city council to name a street or square in her honor, a proposal that has not yet progressed.

In her hometown, Zizurkil, as part of the events commemorating March 8th this year, a mural has been painted in her honor and that of all the women of the town. Local resident Izaro Lizarraga and Arantxa Orbegozo from Tolosa were responsible for the artwork, which includes a phrase by Begoña Gorosperena, a friend of Kaxilda: “Woman! You are the fire that never ends!”, the same phrase inscribed on Kaxilda's tombstone in Biarritz. Gorospe herself participated in the inauguration ceremony of the mural on March 25th.