The artist and restorer Marianne Adler was the daughter of the journalist Heinrich Adler and the illustrator Maria Adler and the niece of the prominent Austrian Social Democrat Victor Adler. Works by Adler, who had attended the Kunstschule für Frauen und Mädchen (Art School for Women and Girls) in Vienna on the recommendation of Gustav Klimt, were shown in 1908 at the Wiener Kunstschau, an art and crafts exhibition by the group around Gustav Klimt and Josef Hoffmann. Some of her works were still to be seen in the 1980s in Schloss Leopoldskron, and in 2010 a charcoal drawing by her was put up for sale. She worked from May 1926 in the restoration workshop at the Kunsthistorisches Museum in Vienna. On 16 March 1938 she was suspended by the provisional director Fritz Dworschak. Ludwig Baldass, the new director appointed after the annexation, reported that her work was excellent from a technical and artistic point of view but that she was "unusually slow". She was dismissed with effect from 1 April 1938 on the grounds of "non-attainment of goals by a contract employee in spite of warning" (BGBl II 1934/312). Adler was given five months' notice. "Racial grounds" also played a role, since her father had been a member of the Jewish Community until 1884. She was able to emigrate subsequently with the help of Kenneth Clark, director of the National Gallery in London, who employed her for a while as a restorer. Life magazine devoted an article in December 1940 to her discoveries while restoring the picture Ecce Homo by Urban Görtschacher. At that time she was already living as Mary Ann Adler in California and working as a restorer for the Huntington Museum in San Marino, but she also took on commissions for other museums and collections. She never completely broke off contact with the Kunsthistorisches Museum in Vienna and corresponded in the 1950s with the director of the Picture Gallery Ernst Buschbeck. She died in California in 1952.
Marianne Adler was acquainted with the Jewish art collector Bruno Jellinek. Before escaping in early 1938, he deposited part of his collection in her apartment on Brahmsplatz. On 17 June 1938, the Devisenfahndungsamt (Foreign Exchange Control Office) informed the Central Monument Protection Authority that an order securing the collection had been issued pursuant to § 24 of the Devisenordnung für das Land Österreich (Foreign Exchange Order for the Province of Austria), preventing its export it in that way. Adler was instructed to hand over the artworks to the transporters Caro & Jellinek. In 1941, the Städtische Sammlungen Wien auctioned some of the collection in the Dorotheum. The Vienna Restitution Commission decided in 2003 that the objects should be returned to the legal successors of Bruno Jellinek.