[3] Thekla had six siblings: the four sisters Anna, Anastasia, Pulcheria, and Maria, whom Theophilos took great pride in,[7] and the two brothers Constantine and Michael.

[9] In the 830s, the eldest sisters Thekla, Anna, and Anastasia were all proclaimed augustae, an honorific title sometimes granted to women of the imperial family.

This event was commemorated through the issue of an unusual set of coins that depicted Theophilos, Theodora, and Thekla on one side and Anna and Anastasia on the other.

[21] The numismatist Philip Grierson comments that dated documents from the time of the coins' minting prove that she was "formally associated with Theodora and Michael in the government of the Empire.

[4] In 857[23] or 858[4] Theodora was expelled from the imperial palace and confined to a convent in Gastria, in Constantinople;[23][24] the monastery had been converted from a house by her maternal grandmother, Theoktiste, likely during the reign of Theophilos.

[27] According to the tradition of Symeon Logothete, a 10th-century Byzantine historian, Thekla was also released and used by Michael III to attempt to make a political deal.

However, Symeon's neutrality is disputed, and other contemporary sources do not speak of this conspiracy, leading several prominent Byzantists, such as Ostrogorsky and Nicholas Adontz to dismiss this narrative.

[31] The historian William Greenwalt speculates on the reasons that drove Thekla to agree to this relationship: resentment for having been unmarried for so long, Basil's imposing physical stature, or political gain.

[26] After Basil murdered Michael III in 867 and seized power for himself, Symeon further writes that Thekla then became neglected and took another lover, John Neatokometes,[28] sometime after 870.

[5] The De Ceremoniis, a 10th-century Byzantine book on courtly protocol and history, states that she was buried in the Monastery of Gastria, where she had been confined earlier, in a sarcophagus with her mother and her sisters Anastasia and Pulcheria.