If a woman's menstrual period exceeds six days, should she fast and make up the days during which the bleeding continued? And should she perform ghusl (ritual bath) and make up the days if drops of blood appear after the menstrual period has ended?

If the usual menstrual period is six days, and then blood appears for four days afterward, this blood is not considered menses according to the Hanbalis unless it occurs three times. In that case, the custom (habitual period) would have changed. If this is the first time, you are not required to make up prayers (qada') or perform ghusl (definition) after every drop, because the blood was not menstrual blood. However, if the bleeding recurs three times, then you must make up for the days that were clarified to have been menses.