Lassalle fragt Herbert nach Sonja. Die Szene ein Salon is a three-act play by the German author Christoph Hein. The play was first performed in 1980 in East Germany and criticizes Marxism. In the 1860s, Ferdinand Lasalle founded the first German labour party (one of the first socialist parties in Europe) but is not very active in the play. His private matters get in the way of his party work, so a delegation of workers needs to be sent away three times during the play.
Lassalle's mother, Ms Lassal (no typo here!), who lives with her son, doesn't seem to have any impact on what is going on; the summary in the German Wikipedia article about the play does not even mention her. However, she is one of only four characters who appears in each of the three acts and she is the first character to appear in the first act, so it is unlikely that she meaningless. We learn early in the play that she secretly steals pieces of cake from the kitchen and that she puts her fingers in the jam in the kitchen; later we even learn that she wets her bed every night. So she is too out of the ordinary to be meaningless, but what does she represent?