Born in Berlin, Silja began her operatic career at a very early age, with her grandfather, Egon Friedrich Maria Anders van Rijn, as her voice teacher.

She sang Rosina in Rossini's The Barber of Seville in Braunschweig in 1956, followed by Micaëla in Bizet's Carmen and Zerbinetta in Ariadne auf Naxos by Richard Strauss.

There is no denying that this is one of the great performances of our time.Additional new roles in the 1960s were Jenny Smith in Weill's Aufstieg und Fall der Stadt Mahagonny), Lady Macbeth in Verdi's Macbeth, Violetta Valéry in Verdi's La traviata, first Liù, then the title role in Puccini's Turandot, Lucy in Menotti's The Telephone, Cassandre in Les troyens (opposite Jon Vickers) and Renata in The Fiery Angel.

In the 1980s, Silja added Lady Macbeth of the Mtsensk District (opposite Chester Ludgin), La Cubana, Regan in Lear, Prinz Orlofsky in Die Fledermaus (with Karita Mattila and Judith Blegen, staged by Maurice Béjart), the Kostelnička in Jenůfa (at the Glyndebourne Festival),[4] Grete in Der ferne Klang, and the Nurse in Die Frau ohne Schatten (opposite Dame Gwyneth Jones as Barak's Wife).

She then assumed the roles of Agave in The Bassarids (at Carnegie Hall), Ortrud in Lohengrin (in Robert Wilson's production), Herodias in Salome, Anna I in Die sieben Todsünden, Klytämnestra in Elektra, Jocasta in Œdipus rex (opposite René Kollo), Mother Marie of the Incarnation in Dialogues des Carmélites, Pierrot lunaire, Judith in Bluebeard's Castle, Countess Geschwitz in Lulu, Madame de Croissy in Dialogues des Carmélites (her Teatro alla Scala debut, under Riccardo Muti, 2004; three years later she sang in Jenůfa there), Míla's Mother in Osud, the Comtesse in Pique-dame, and the Witch in Hänsel und Gretel.

I’m very thankful that it happened and it’s a great help and strength to me.”[6] In January 2013, she sang the role of the Grandmother ("Babulenka") in The Gambler, in Frankfurt, in the production by Harry Kupfer, and in 2017 she performed Schoenberg's Pierrot lunaire and was the narrator in Gurre-Lieder in Hamburg, conducted by Kent Nagano.