Born on 12 June 1928 in the Eich district of Luxembourg City, Koltz began to write fairy stories in the 1950s mainly in German and Luxembourgish. She has also worked as a translator. Many of her works have been translated into English, Spanish and Italian. She is considered to be Luxembourg's most important contemporary poet.
Since 1963, the Journées littéraires de Mondorf (Mondorf Literary Days) have created links between Luxembourg writers and the international scene. In 1995, the Mondorf Literary Days were revived, representing all literary genres so as to provide a wide range of authors with a platform for their works.