Having studied in Johannesburg and in Vienna, she was a member of the Vienna State Opera from 1956 until 1978. She was a guest to the Royal Opera House, Covent Garden and the Glyndebourne Festival. After 1978, she continued to perform in South Africa.

Coertse sang the soprano part in Bach's "Matthäus-Passion" at Fritz Wunderlich's first appearance at Vienna in 1958, when he did the tenor arias with Julius Patzak singing the Evangelist. In 1958, Coertse and Wunderlich again worked together at the Aix-en-Provence festival in "Die Zauberflöte". In 1965, she sang Konstanze in Werner Düggelin's controversial production of "Die Entführung aus dem Serail" at the Vienna State Opera which also featured Fritz Wunderlich as Belmonte.

Her roles include

• Konstanze (Mozart: Die Entführung aus dem Serail)
• Donna Anna.(Mozart: Don Giovanni)
• Königin der Nacht (Mozart: Die Zauberflöte),
• Zerbinetta (Strauss: Ariadne auf Naxos)

Recording with Fritz Wunderlich:

Pfitzner

• Palestrina