Both Julie and her sister Charlotte were active as courtesans or high class prostitutes from an early age.
Among her clients were a certain Müller, secretary at the German legation in Stockholm, whom she reportedly used as a spy with the Russian ambassador, Andrey Razumovsky.
In 1780, she became the mistress of riksråd count Carl Sparre, who was known as a libertine, especially after having been widowed by Ulrika Strömfelt; from 1785, she lived openly with him at his Lustschloss Bellevue, officially with the title house keeper.
Sparre's political advisories accused him of having wasted the funds he collected through his office on Julie Eckerman, who was said to control his actions and accepted commissions from supplicants who wished to affect him.
In 1789, Sparre discontinued the relationship because he planned to remarry, and arranged a marriage for Eckerman with Nils Björkegren, who was described as a beautiful youth and whom he had made mayor of Linköping.