If a woman returns to prayer after seeing a sign of purity, then the blood, with the characteristics of menstrual blood, reappears, is she sinful, and what should she do in this situation?

If the blood returns within a period not exceeding fifteen days (the maximum duration of menstruation according to the majority of scholars), then it is menstrual blood. If the woman sees purity, she should perform ghusl (definition) and pray, and her husband is permitted to have intercourse with her. If the blood returns, she is considered menstruating again until it stops. It is not permissible to abandon prayer during the period of purity that interrupts the days of menstruation, and this is what many scholars have favored.