On marrying her fellow student René Bertholo [pt] (1935–2005), in 1957 she presented an exhibition with him at Lisbon's Galeria Diário de Notícias.

There the couple published the experimental art journal KWY (1958–1963), creating a movement which included the Bulgarian Christo Vladimirov Javacheff, the German Jan Voss, and Portuguese artists including António Costa Pinheiro [pt], José Escada, João Vieira and Gonçalo Duarte.

[1][3] Inspired by Árpád Szenes, Castro concentrated on abstract painting but in 1961 followed the Nouveaux Réalistes, creating collages consisting of real objects such as printing press letters or bottle tops in silver-painted boxes.

[1] From 1973, Castro worked with her lifelong partner Manuel Zimbro, creating shadow theatre shows which were widely presented in South America and Europe.

[7] The President of Portugal, Marcelo Rebelo de Sousa, expressed his regret at Castro's death, whom he described as "one of the most unmistakable Portuguese artists".