Born in Vaduz, Weirather is the daughter of former World Cup ski racers Harti Weirather of Austria and Hanni Wenzel of Liechtenstein (and the niece of Andreas Wenzel). Her mother Hanni won two overall World Cup titles (1978, 1980) and two Olympic gold medals (1980), four Olympic medals overall; uncle Andreas won the men's overall World Cup title in 1980 and 2 Olympic medals. Her father Harti won the season title in downhill in 1981 and was world champion in 1982.