Answered by Shaykh Amjad Rasheed
Zaid owed money to Amr. Zubayda came and paid off the debt, without the permission or request of Zaid. Does she have the right to demand that Zaid pay her back?

In the Name of Allah, Most Merciful and Compassionate. May His blessings and peace be on His Beloved Prophet, the best of creation, and his family, companions, and followers
Walaikum assalam wa rahmatullah,
No, she does not have the right to demand that he pay her back.
Amjad Rasheed
(Translated by Faraz Rabbani)
[Faraz notes: this is the legal ruling’. Depending on circumstances, it may be from proper behavior, excellence, or even plain dignity to pay her back. If Zubayda was somehow cheated or tricked into paying back, then it would fall under the Prophetic warning that, “Whoever cheats is not of us.”]