Her father, Friedrich Schlemm, was a chorister at the Oper Frankfurt. Schlemm studied in Berlin with Erna Westenberger and made her debut 1946 at the Halle Opera House in Halle an der Saale as Nanette in Lortzing's Der Wildschütz. In 1949 she joined the Komische Oper Berlin, where she remained until 1961 and is a lifelong Member of Honour. During that period her roles included Susanna, Marenka, Donna Elvira, Desdemona, Manon Lescaut, Octavian, Arabella among others. She also sang at the opera houses of Cologne, Hamburg, Dresden, Frankfurt, Stuttgart, Munich, and at the Bayreuth Festival and more.
A superb singing-actress and highly versatile artist, Schlemm was equally at home in comic and dramatic roles. She was married to conductor Wolfgang Rennert.