There, she was seen as a prostitute in August Strindberg's Meister Olaf in a production of Ferdinand Gregori [de], as Lesbia in Felix Hollaender's staging of Friedrich Hebbel's Gyges und sein Ring, as Recha in Lessing's Nathan the Wise, and as sister Martha in Gerhart Hauptmann's Hanneles Himmelfahrt.

In addition to these roles, she played under Marion Reinhardt's direction of Georg Büchner's Danton's Death, a maid Sophie in Friedrich Schiller's Intrigue and Love and Desdemona in William Shakespeare's Othello, and Jessica in The Merchant of Venice.

Her most famous roles include Gesine von Orlamünde in Chronicles of the Gray House, and Countess Dusy Told, the wife of a millionaire in Fritz Lang's Dr. Mabuse the Gambler (1922),[4][5] in which the title character abducts and abuses her.

[1] Other major productions in which Welcker participated were Richard Oswald's Lady Hamilton, and Carl Froelich's Luise Miller (after Schiller's Intrigue and Love).

In low-budget productions such as Die Geisha und der Samurai and Eine Frau mit Vergangenheit, she played the lead role.