How does a woman ascertain ritual purity (ṭahāra) from menstruation, given that her menstrual period lasts from 5 to 7 days, and she observes dryness or brown/yellowish discharge after the cessation of blood, which causes her confusion regarding performing the ritual bath (ghusl) and repeating prayers?

A woman knows her purity by two signs: the white discharge (al-Qassah al-Bayda') or dryness (al-Jufuf). Dryness is when she inserts a piece of cotton and it comes out clean. Yellowish or brownish discharge connected to menstruation is considered menses, but what appears after seeing purity is not considered menses. So, if a woman sees yellowish or brownish discharge when inserting cotton, she is still menstruating until she sees purity. If she sees purity by dryness, she must perform ghusl (ritual bath). Any yellowish or brownish discharge she sees after that is not considered menses, and she does not become menstruating again unless blood returns at a time suitable for menstruation.