The already good relations between the Albertine and Ernestine branches of the House of Wettin were reinforced already in 1686 when Duke John George II of Saxe-Eisenach arranged the marriage of his older sister, the Dowager Margravine of Brandenburg-Ansbach with John George IV, Elector of Saxony. However, the union was a complete failure and ended childless. Both spouses died in 1694 and 1696, respectively. With John George IV's brother and successor, Frederick August I already married, Duke John George II had to search another marriage to bond again both Wettin branches. In this way, ten months before his own death Duke John George II arranged the marriage of his younger sister Fredericka Elisabeth with Johann Georg, Duke of Saxe-Weissenfels. The wedding took place in Jena on 7 January 1698. They had seven children, of whom only one survive adulthood:
In addition to the reform policies of her husband in the Querfurt-Weissenfels tiny Duchy, Frederica Elisabeth brought considerable social impulse. So they worked towards the adoption of a charity order in 1700 and founded on her birthday in 1710 an orphanage in Langendorf, whom she continued to supported financially until her death. Particularly attracted to Frederica Elisabeth was the popular jardin à la française. As a gift to her, Duke Johann Georg built the so-called Hermitage between Weissenfels and Langendorf, the Klein-Friedenthal, a zoo at Neuenburg Castle and the garden at the Leisslinger Wiese. Her husband was also prone to great courtly splendor, under which he specially made for Fredericka Elisabeth in 1710 the construction of an expensive small river port in Weissenfels. With a small flotilla of 15 ships, were organized pleasure cruises on the Saale. After her husband's death and the accession of her brother-in-law Christian to the Ducal throne in 1712, she received Dryburg Castle in Langensalza as her Wittum, where she ordered the construction of a royal park before finally moved there in 1717. In addition to the changes in the park, she made several structural changes in the Castle and nearby town. Fredericka Elisabeth died in Dryburg Castle aged 61, and was buried in the Schlosskirche, Weissenfels. Since her body had to be firstly embalmed before his long journey to Weissenfels, the extracted entrails were buried separately in an urn.