Princess Stephanie of Windisch-Graetz's mother was a member of what political party?
Princess Stephanie of Windisch-Graetz: Princess Stéphanie of Windisch-Graetz (April 4, 1909 in Ploskovice, Bohemia – May 29, 2005 in Uccle, Belgium) was the daughter of Prince Otto Weriand of Windisch-Graetz (1873–1952) and Archduchess Elisabeth Marie of Austria (1883–1963), only child of Crown Prince Rudolf of Austria and Princess Stéphanie of Belgium. Archduchess Elisabeth Marie of Austria:  Later nicknamed "The Red Archduchess", she was famous for becoming a socialist and a member of the Austrian Social Democratic Party.
Austrian Social Democratic Party