Assia was born in Rupperswil, Aargau, and began her stage career as a dancer, but changed to singing in 1940 where she met her first musical success in 1950 with "O mein Papa".

[4][5] In 2005, Assia performed at the Congratulations: 50 Years of the Eurovision Song Contest event.

In September 2011, Assia entered her song "C'était ma vie", written by Ralph Siegel and Jean Paul Cara, into the Swiss national selection Die grosse Entscheidungs Show for the Eurovision Song Contest 2012 in Baku, Azerbaijan.

There were rumours of Assia representing San Marino, but it was announced on 30 January 2013 that Valentina Monetta would do so.

Assia married Johann Heinrich Kunz on 11 January 1957 in Zürich.