Charlotta Eckerman was from 1774 active as a courtesan. In 1779, she was made the official mistress of the king's brother duke Charles, the future Charles XIII of Sweden. Rumour claimed that Charles took Eckerman as a mistress upon the advice of his brother, Prince Frederick Adolf of Sweden, who thought it more polite to Charle's consort than his first choice; countess Maria Sophia Rosenstierna, who was the courtier of his consort. The relationship caused a scandal because of sympathy toward the consort of Charles, Hedvig Elisabeth Charlotte of Holstein-Gottorp, who was very popular. Duke Charles tried to influence king Gustav III to take an official mistress, and Eckerman suggested the French adventurer Madame Monzouve (or de Monzouvre), but the plot does not seem to have succeeded. In 1781, Charles ended the connection; it was rumoured that the relationship ended because of the scandal, but in reality, it was more likely because Charles regarded it as necessary after having became inducted in to the Freemasons.
In 1781, Eckerman became involved in a conflict with the king, Gustav III of Sweden. Eckerman was disliked by the king, as it was said, because she did not admire him and because she had a talent for caricatureing the current ideals. When her affair with the king's brother ended and she could no longer count on his protection, the king arranged for her dismissal from the Opera and had her banished from Drottningholm. Furthermore, he ordered Baron Carl Sparre, the governor of the city of Stockholm, to have her arrested and sent to jail. As a reason, he claimed that she had given birth to a child and murdered it in secrecy, and that she had taken part in the spreading of rumours regarding the legitimacy of the heir to the throne. There where at the time many rumors that the crown prince was fathered by the stable master Count Adolf Fredrik Munck af Fulkila on the orders of the king, rumors which were spread by the king's own mother, Louisa Ulrika of Prussia, and increased when Munck were given gifts by the king and the queen. Sparre, who was the lover of Eckerman's sister Julie, was aware of the king's dislike of Eckerman. Sparre investigated the accusations and could find nohing to indicate that she had committed child murder. Charlotte Eckerman denied the accusation that she was to have spred rumours regarding the crown prince's legitimacy, and claimed that it was the king's page, Georg Johan De Besche as the guilty party. De Besche was to have said, that the gift the queen had given to Munck was well worthy of the birth of an heir to the throne.
Sparre refused to arrest her, and pointed out that it was against Swedish law for a monarch to threaten the freedom of a citizen without a legal verdict from a court. The whole affair ended in silence. Eckerman was not sent to jail, and the king did not mention it further. Eckerman left the country shortly afterward, possibly banished by the monarch.