What is the ruling on completing the six days of Shawwal for a woman who started menstruating in the afternoon, and does not have an opportunity to complete her fasting on other days?

You were obligated to break your fast as soon as menstruation began, because a menstruating woman's fast is neither valid nor permissible for her, as the Prophet, peace and blessings be upon him, said: "Is it not true that when one of you menstruates or gives birth, she neither prays nor fasts? That is a deficiency in her religion." You do not owe a make-up fast for that day, as the fast was nullified by a legal impediment.