Musannaf Ibn Abi Shayba 9:633

Ibn al-Mubarak narrated to us, from Hanzala, who said: I heard Tawus, and he was asked about a slave woman who is emancipated while she has a free husband: "Does she have the choice [to annul the marriage]?" He said: "I have no knowledge [of that], but if she were under a slave, she would be given the choice."