What is the ruling when a wife asks her husband, 'Divorce me and my co-wife for one thousand,' and he divorces both?

Primary text

If a wife tells her husband to divorce both her and her co-wife for a sum of one thousand, and he divorces them both, the divorce is irrevocable (ba'in) for both, and the wife who offered the consideration is obligated to pay the agreed-upon amount. This ruling is based on the validity of Khul' (redemption divorce) with a non-husband (the co-wife being involved in the condition).