Inspired by the November Revolution and her meeting with political satirist Kurt Tucholsky, Valetti began performing in cabarets.

She directed the cabaret Rakete for a time, then launched another cafe of her own, the Rampe, which hosted the works of revolutionist poet and singer Erich Weinert.

[2] In 1928 she performed as Mrs. Peachum in the original cast of Bertolt Brecht's Threepenny Opera, which was staged under the direction of Erich Engel at Berlin's Theater am Schiffbauerdamm.

Her age and sturdy mien ensured that she acted mostly in motherly roles, as in the 1925 film Die Prinzessin und der Geiger (The Princess and the Violinist), in which she played a 46-year-old grandmother.

In Josef von Sternberg's 1930 film Der Blaue Engel (The Blue Angel) she plays the wife of the magician, Kiepert (Kurt Gerron).