At the age of just sixteen, Luise Kremlacek started working in 1920 as a saleswoman at Galerie Würthle & Sohn Nachf. In 1939 the gallery owner Lea Bondi-Jaray, who was of Jewish origins and subject to increasing persecution from the Nazi regime, had to emigrate. Thereafter, Friedrich Welz, who had Aryanized the company, made Kremlacek manager, and it operated from 1939 to 1948 under the name Galerie Welz. After restitution to the former owner Bondi-Jaray, she ran the gallery from 1949 again under the name Würthle, and Kremlacek continued to work there until she retired in 1982.
While working in the art market, Kremlacek began herself to collect, in particular works by younger artists, "living art", as the art magazine Parnass called it in an obituary. Some of the works had been dedicated to her by Friedrich Welz for her collaboration or by artists themselves for whom she had occasionally modelled. The extent of her private collection can be seen from the auction of her estate in 1991 in the Dorotheum for the benefit of the artists' self-help association Vereinigung Künstler helfen Künstlern. Among the 220 items were works by Herbert Boeckl, Josef Dobrowsky, Anton Faistauer, Gustav Klimt, Alfred Kubin, Oskar Kokoschka, Egon Schiele and Franz von Zülow. The catalogue shows the provenance of some of the works. Kremlacek also acquired artworks from collectors such as the Viennese dentist Heinrich Rieger or the doctor Oskar Reichel, who had sold them via Galerie Würthle/Welz to finance their escape, as she testified in 1948 during a hearing at Salzburg Landesgericht (provincial court) regarding the restitution proceedings against Friedrich Welz. Two of the works by Egon Schiele in her estate are proven to have come from Heinrich Rieger's collection, and the IKG (Vienna Jewish Community) suspects that four other works also belonged to Rieger's collection. Their whereabouts are currently unclear. A drawing by Kokoschka acquired by the Albertina through the art market from Kremlacek's estate bears the previous provenance of Oskar Reichel and is therefore the object of provenance research.