[1][2] Her younger sister was the Austrian economist, women's rights activist, journalist and politician Käthe Leichter.
She studied piano under Richard Robert, composition under Karl Weigl and musicology under Guido Adler.
Vally married Karl Weigl in 1921, and after the National Socialists took power in Austria in 1938, the couple emigrated with their son to the U.S. with assistance from the Quaker Society of Friends.
Vally directed research projects at Mount Sinai Hospital's psychiatric division and the Hebrew Home for the Aged, and in the 1950s published a number of articles in the field of musical therapy.
[6] Vally Weigl composed a large number of works for orchestra and solo instruments.