She could claim royal blood through her descent from her great-grandfather King Christian III of Denmark, but her parents were of lower rank: Philip, Duke of Schleswig-Holstein-Sonderburg-Glücksburg, and Sophia Hedwig of Saxe-Lauenburg.

In 1653, Dorothea married Christian Louis, Duke of Brunswick-Lüneburg, brother-in-law of King Frederick III of Denmark.

In 1665, her first spouse died, and she moved to Herzberg Castle as a widow's seat while her brother-in-law George William followed him as the reigning Duke of Luneburg in Celle.

Asked by the (lutheran) Prussian Estates about her religious convictions, she gave them a detailed "Confession of Faith" in early 1669, which began with the sentence: "I do not believe what the Pope orders, not even in all the parts that Luther, Zwingli, Beza and Calvin write (...)."

Today it is a museum of the Prussian Palaces and Gardens Foundation Berlin-Brandenburg, whose exhibition provides information about the life and work of Dorothea.

The suspicion that Dorothea worked towards a division of Brandenburg-Prussia in order to secure an income for her sons or even to cobble together states of their own for them;[4] this is regarded as refuted by historical scholarship, but spoiled her reputation for a long time.

Posthumously, the impression was wrongly given that she wanted to make an agreement with France, accepted a division of the country and thus called into question the rise of Prussia to become a great power.