In 1455 she was second wife of Ulrich I Cirksena, who had been Count of East Frisia since 1454. Between 1457 and 1465, they had six children: Heba, Gela, Enno I, Edzard I the Great, Ucko and Almuth. Theda brought, among other claims, Oldersum into the marriage, which considerably weakened the ruling chief Wiard of Oldersum.
