What is the ruling on prayer for a woman whose menstrual period lasted 8 days, then was intermittent for a week between purity and light spotting (istihada), then heavy bleeding like menstrual blood returned?

If the duration of bleeding, including any intervening periods of cleanness, exceeds fifteen days, the woman is considered to have Istihada (non-menstrual bleeding). She should refer to her previous habit and count that as menstruation, and anything beyond that is Istihada. If she does not have a previous habit, she should differentiate between menstrual blood based on its characteristics (color, smell, pain) and other types of blood. If she has neither a habit nor the ability to differentiate, she should consider six or seven days as menstruation, and anything beyond that is Istihada. She must perform Ghusl (ritual bath) after the menstrual period ends and perform Wudu' (ablution) for every prayer after its time has begun. She is subject to all the rulings applicable to ritually pure women.