She was born to Kai and Kaja Gnatt, née Olsen, a family of dancers living in Baden, Austria.
Kirsten's mother encouraged her, and her brother Poul, to train as dancers.
[1] She entered the school of the Royal Danish Ballet at the age of 22, and was associated with that troupe throughout her career.
Her farewell performance was in 1962, where she danced the Ballerina Doll in Petrouchka by Michel Fokine.
[3] She was first married to Børge Ralov, then later to Fredbjorn Bjornsson; both Danish dancers.