During her mid-20s Welcker ended her career as a film actress and in 1930 retired from the stage as well.
In 1941 she became active for the Red Cross.
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), in which the title character abducts and abuses her.
She played the character of Queen Margaret in the controversial film The Women House of Brescia. The film was rejected by the British Board of Film Classification on grounds that it depicted prostitution.
Her first role was of an angel in the film Hans Trutz im Schlaraffenland directed by her stage partner Paul Wegener.