I say, and with God's success: It is not permissible for her to fast a voluntary fast without her husband's permission, except if he is traveling or is ill with a sickness that prevents him from being close to her. And when he is present, she should not prolong the prostration, and in his absence, she can pray as she sees fit. She should be patient and seek reward from God Almighty, and frequently pray for her husband, and do good to him, so that perhaps God Almighty will guide him to His path, and God knows best.