Is a woman obligated to fulfill a vow to fast the first nine days of Dhul-Hijjah every year, even with her husband's objection and her inability to fast due to health reasons, or is it permissible for her to offer expiation for it or make up the fasts intermittently?

Making a vow (nadhr (definition)) is disliked (makrooh) or forbidden (haraam) to initiate because it obligates a Muslim to something they might not be able to fulfill. However, if the vow is an act of obedience, then it is obligatory to fulfill it, based on the Prophet's (peace be upon him) saying: "Whoever vows to obey Allah, let him obey Him." Accordingly, if a woman vowed to continuously fast the first nine days of Dhul-Hijjah, she must fulfill it, and her husband is not permitted to prevent her from doing so. If she is unable to fast in a particular year due to illness or weakness, she should offer expiation (kaffarat yameen) for that year and fast in the years when she is able. If these days coincide with her menstrual period, she is excused from fasting.