She served as Chief Court Mistress to queen Catherine Jagellon and, after her death, to Princess Anna Vasa of Sweden.
Karin was the daughter of riksråd Göran Eriksson Gyllenstierna of Fogelvik (- 1575) and Kerstin Nilsdotter Grip (- 1538).
She became a widow in 1554, and gave birth to her son Nils Nilsson Natt och Dag (1554-1613) posthumously.
In 1594, her rights were for a second time confirmed over that of the relatives of her late fiancé, but again without the feud being put to an end.
After the death of the queen in 1583, she was given the equivalent position at the court of Princess Anna Vasa of Sweden.