How many movies have Hildegard Grethe and Lotte Neumann collaborated on?

They have worked on 2 movies together! Their first movie together was Robert Koch, der Bekämpfer des Todes (1939) while their highest rated movie together was Friedrich Schiller – Der Triumph eines Genies (1940). They have not worked together since Friedrich Schiller – Der Triumph eines Genies (1940).