She was the third wife of the abusive Archduke Karl Ludwig of Austria and stepmother to the ill-fated Archduke Franz Ferdinand. She was prominent in seeing to the morganatic marriage of Franz Ferdinand to Sophie Chotek. Franz Ferdinand and Sophie were assassinated by Gavrilo Princep at Sarajevo on 28 June 1914. Austria sought to punish Serbia and things got out of hand as national rivalries led to World War I that cost the Habsburgs and Hohenzollerns their thrones and many Romanovs their lives. Infanta Maria Teresa's Wikipedia article is here.