Until 1938 Helene Silverio was employed at Galerie Harding, Kärntnerstraße 16 in Vienna's 1st district, and was already engaged before the annexation of Austria to Nazi Germany to Arnold Harding, one of the two owners. In early 1939 the Property Transaction Office authorized her to take over the gallery from Arnold Harding. The other partner, Alfred Harding, had fled to Czechoslovakia shortly after annexation to avoid persecution. Silverio was never a member of the NSDAP but became a member of the Reich Chamber of Fine Arts at the end of July 1938 so as to be able to operate as an art dealer. The gallery was renamed Galerie Helene Silverio in 1940 with her as the sole proprietor. Both the previous owner Arnold Harding and Silverio were subject to attacks and attempts at blackmail by the art dealer Eduard Nierscher, who attempted unsuccessfully to gain title to the company. Nierscher, who had been employed in the gallery until 1935, knew of the relationship between Silverio and Arnold Harding, which under the Nazi laws constituted the criminal offence of "racial defilement". Draconian punishment was also meted out for "disguised takeover". In fact, this was one of the few cases of "fictitious Aryanization" in the art and antiques business. Silverio hid Arnold Harding from November 1941 until the end of the Second World War in her apartment at Weihburggasse 4 in the 1st district, not far from the gallery, to protect him from deportation. She helped other Jewish persecutees as well, such as Gertrude Spiegler, married name Neuwirth (1909–1965), who was also hidden in her apartment and the attached storerooms. Silverio had to organize food on the black market and also to recruit a few friends and acquaintances so as to be able to look after them.

Helene Silverio and Arnold Harding married in May 1945, just after the end of the Second World War. The background to the proceedings instigated by Hans Lion, an Austrian art dealer persecuted as a Jew and living in Nice, against Helene Silverio for the return of the Klimt painting The Fishes is unclear. In its judgement of 14 January 1952, the restitution commission at the provincial court for civil law matters in Vienna rejected Lion's claim as being unfounded. After the war Helene Harding continued to manage the gallery – renamed Galerie Helene Harding in 1949 – as sole proprietor. She relinquished her trade licence in November 1974, just under a year after her husband's death.