How can a woman deal with her menstrual period, which ranges between 8 and 9 days, especially if she is now experiencing istiḥāḍah (non-menstrual vaginal bleeding)?

If a woman with istihadah (non-menstrual bleeding) has a previous customary period, she refrains from prayer for the duration of her custom, then performs ghusl (ritual purification) and prays. Any bleeding beyond that is istihadah. If her custom is not fixed—for example, if she menstruates sometimes for eight days and sometimes for nine days—she observes the most consistent part of her custom (eight days). On the ninth day, she examines the blood: if it resembles normal menstrual blood, then it is menstruation; otherwise, it is istihadah. If she cannot distinguish and nothing becomes clear to her, then she observes nine days, because the default is that what was remains as it was, and a change is not determined merely by doubt.