Born in Stettin (today Szczecin), Kirschstein received her training at the Robert Schumann Conservatory in Düsseldorf, where her instructor was Franziska Martienssen-Lohmann.

Kirschstein began her career at the Städtische Oper Berlin in 1958, and from 1960 to 1963 she was on the roster of the Stadttheater Kiel; from 1965 to 1968 she was a member of the company at the Augsburg Opera.

She sang at the Salzburg Festival the soprano part in Mozart's Requiem in 1961, and appeared there in 1970 as the First Lady in his Die Zauberflöte.

[3] She sang the soprano part in Helmuth Rilling's 1966 recording of Bach's drama per musica Schleicht, spielende Wellen, BWV 206, alongside Margarethe Bence, Kurt Equiluz and Erich Wenk.

[6] She recorded Beethoven's Missa solemnis with Günter Wand conducting the chorus and orchestra of the Gürzenich in Cologne, alongside Jeanne Deroubaix, Peter Schreier and Günther Morbach.