What is the ruling regarding a woman who vowed to fast six days of Shawwal every year and is now unable to do so: Is she obligated to offer expiation (fidyah) every year or only once?

If a woman vows to fast specific days each year, she is obligated to fulfill her vow as long as she is able. If she becomes unable due to a continuous excuse, such as an illness from which recovery is not expected, she must offer an expiation for breaking an oath (feeding ten poor persons or fasting three days), and feed one poor person for each day she vowed to fast. However, if the inability is due to a temporary impediment that is expected to be removed, she must wait until the impediment is gone and then fast.