What is the ruling regarding a single drop of blood that appeared after purification, and what is the ruling concerning the days during which she was purified, and how much fasting must she make up?

A woman must perform ghusl, pray, and fast if she sees purity (cessation of bleeding). Her fast is valid. If the blood returns within the menstruation period (15 days), she is considered to be menstruating. The Hanbalis hold that blood that appears outside of the accustomed time is not considered menstruation unless it occurs three times. The questioner's fast after the first four days was valid, and she is not required to make it up. As for the drops of blood she saw afterward, according to the Hanbalis, this is considered istihadah (non-menstrual bleeding), and her fast is valid, and she is not required to make it up unless it recurs. However, according to the view that all blood a woman sees during the menstruation period is considered menstruation, her fast during those days is not valid. The more cautious approach is to make up the days on which she saw drops of blood, to avoid dispute and clear one's conscience, and similarly to make up the prayers performed after seeing drops of blood if she had not performed ghusl for them.