In 1577, Sybilla's older sister Anna Maria was relieved from her post as Imperial abbess of Gernrode and Frose in order to marry Joachim Frederick of Brieg; under pressure from their father, the chapter elected the 13-year-old Sibylla as her successor.

In 1581, Sibylla was relieved from her post in order to marry Frederick, Count of Mömpelgard and heir apparent of the Duchy of Württemberg.

Marital fidelity was not compatible with Frederick's view of the prerogatives of an absolutist monarch, and Sibylla accepted his infidelities without complaint.

After this, the couple virtually lived apart, and Frederick did not take Sybilla with him on his frequent travels to France, Italy, and England.

To veil her interest in the dubious discipline of alchemy, she explained her activity as gathering an herbal collection for the production of medicine for the poor.