Wikipedia: Thekla is considered a daughter of Bardanes Tourkos and his wife Domnika. Her parents are considered to be Armenians.
According to Theophanes the Confessor, Thekla was the daughter of an unnamed strategos of the Anatolic Theme, where Michael served. On this account, her father has been identified with the general and later rebel Bardanes Tourkos. Michael, along with Leo the Armenian and Thomas the Slav, were close associates of Bardanes, although during his revolt in summer 803, both Michael and Leo deserted him.
Thekla and Michael had only one known son, the Emperor Theophilos (813 20 January 842). The existence of a daughter called Helena is possible but there is a contradiction between different sources. Helena is known as the wife of Theophobos, a patrician executed in 842 for conspiring to gain the throne for himself. George Hamartolus and Theophanes report him marrying the sister of the Empress Theodora. Joseph Genesius records Theophobos marrying the sister of the Emperor Theophilos. Whether Helena was sister or sister-in-law to Theophilos is thus unclear.
In 820, Leo V accused his former comrade-in-arms Michael of conspiring against him. Michael was imprisoned but managed to escape. Michael organized the assassination of Leo in the cathedral Hagia Sophia on Christmas, 820. Leo had entered the cathedral unarmed and was thus unable to successfully defend himself. Michael succeeded him as Emperor with Thekla becoming the new Empress.
Her term as Augusta was brief and unremarkable. She died c. 823. Michael procceeded to marry Euphrosyne, a daughter of Constantine VI