I say, and with God's success: If the blood that returns to her is within ten days from the first sighting of the blood, then it is menstruation, and she must refrain from prayer and fasting. However, if the total number of days she saw blood, then purity, then blood exceeds ten days, what exceeds ten days is considered irregular bleeding (istihada), and she should pray and fast, and make up for what exceeds her previous habit in menstruation. And God knows best.