Born in Graz, Behle studied voice there and in Rome for six years. In parallel, she also studied history and philosophy at the University of Graz. Her first engagement as a lyric mezzo-soprano was in 1968 at the Badisches Staatstheater Karlsruhe, where she performed several trousers roles.[2] In 1971, she married an oboist of the NDR and only performed in guest roles, such as Dorabella in Mozart's Così fan tutte at the Stadttheater Klagenfurt, as Cherubino in his Le nozze di Figaro at the Theater Hagen, and as the Gymnasiast (schoolboy) in Berg's Lulu in Lisbon and Graz. When their son Daniel was born in 1974, she took a position as first alto in the NDR Chor to have more time for her family.[3] During that period, she performed as a soloist in concerts and recitals.[2]
On 9 February 1992, she participated in the premiere of Wolfgang Rihm's Die Eroberung von Mexico at the Hamburgische Staatsoper.[2] Other roles in contemporary opera included Regine in the German premiere of Rolf Liebermann's La Forêt (The Forest) at the Schwetzingen Festival in 1988 and repeated at the Oper Frankfurt, Kassandra in Aribert Reimann's Troades, and Agave in Henze's Die Bassariden in Hamburg and the Bavarian State Opera.[3] In 2017, she appeared as Sara in the premiere of Giorgio Battistelli's opera Lot at the Staatsoper Hannover, alongside Franz Mazura as Abraham.[4]