In 1956, Bjoner made her first professional appearance singing the roles of the Third Norn and Gutrune for a radio broadcast of Richard Wagner's Götterdämmerung produced by the Norwegian Broadcasting Corporation and starring Kirsten Flagstad as Brünnhilde. In 1957 she made her stage debut as Donna Anna in Mozart's Don Giovanni with the Norwegian National Opera; reprising the role later that year for her debut at the Wuppertal Opera.
In 1956, Bjoner made her professional singing debut by performing the roles of the Third Norn and Gutrune in a radio broadcast of Richard Wagner's Götterdämmerung, featuring Kirsten Flagstad as Brünnhilde. In 1957, she debuted on stage as Donna Anna in Mozart's Don Giovanni with the Norwegian National Opera, later repeating the role at the Wuppertal Opera that same year.