Born to Johan Jacob Ehrensvärd and Anna Maria Mannerheim, she married "riksråd" count Gustaf Adolf Hjärne in 1739. She and her spouse were both known sympathizers of the Hats. During the Age of Liberty, the Hats and Caps often maneuvered to have their sympathizers placed in court offices, and when the office of senior lady in waiting to the crown princess (from 1771 queen) Sophia Magdalena was to be permanently filled after Ulrica Catharina Stromberg in 1766, the Hats managed to have Hjärne appointed to the office. The appointment was however mostly formal: it was understood that Hjärne would only serve during grander occasions, and that the office would in practice be performed by her deputy (first Ernestine Palmfelt, from 1767 Charlotta Sparre).