When the dowager queen Louisa Ulrika died in 1782, she entrusted Forssberg to her daughter, Princess Sophia Albertina, and asked her to see to her well-being.

[2] The letter claimed Forssberg was born in the seventh month as the daughter of king Adolf Frederick and was left in the care of a merchant.

[2] The letter was written by an anonymous woman who assured her that Forssberg was her sister but that her foster mother would never reveal anything, and that Louisa Ulrika had made a promise to Adolf Frederick that this fact was not to be revealed during the lifetime of Gustav III of certain reasons, and that Louisa Ulrika would have arranged a marriage for Forssberg to a noble if she had not died before.

[2] On 30 November, Sophia Albertina advertised, in discreet wording, in the paper Dagligt Allehanda to search the identity of the unknown writer of the letter.

[2] Sophia Albertina was by now herself convinced that Forssberg was her sister[2] and revealed the affair to the regent de facto, Gustaf Adolf Reuterholm, and the royal family.

The queen was informed of the secret, but out of friendship for her maid of honor, who had a good name for virtue and good customs - perhaps also in reference to the utter jealousy, which Her Majesty had displayed in the matter of the charming actress and dancer m:lle Dulondel, with whom the King had a son called Fredriksson, a jealousy which caused the exile of m:lle Dulondel from the realm - the queen promised her husband to care for the child under the vow of secrecy.

[3] Sophia Albertina admitted that she believed Liewen was the mother of Forssberg but that she would have like to have kept it a secret and that she was surprised that everyone seemed to suspect the same.

[1] Forssberg was engaged to count Carl Edvard Gyldenstolpe,[1] who broke the engagement in 1798 (he married Vilhelmina Gyldenstolpe, daughter of the husband of Lolotte's alleged mother Ulla von Liewen), and in January 1799 to count Gustaf Harald Stenbock, courtier of Sophia Albertina, who had assisted in the investigations.

[1] The favoritism of the princess gave rise to the rumour that Forssberg was in fact the secret child of Sophia Albertina herself.

The truth of her parentage is unconfirmed, but it is considered likely that she was the secret illegitimate daughter of king Adolf Frederick and Ulla von Liewen.

In 1854 her son inherited Sundby Manor at Ornö, which as entailed property remained in his line to the present day.