Born in Salzburg, Hagen began to learn music at the age of six with her father, who was at that time concertmaster of the Mozarteum Orchestra of Salzburg. She then continued her studies at the Musik Hochschule of Salzburg with Helmut Zehetmair and at the Musik Hochschule of Hanover with Hatto Beyerle. During her studies she won several prizes, including the Budapest International Viola Competition in 1984.[1]
Hagen is a founding member of the Hagen Quartet, along with her siblings Lukas, Angelika (later replaced by Rainer Schmidt) and Clemens. The quartet has performed across the world.[2]