Is awaiting the white discharge a valid sign of purity, and is performing ghusl on the eighth and ninth days correct based on the presence of a slight dry period? If ghusl was performed at an incorrect time, must the prayers be repeated? Is brownish discharge outside the usual days of menstruation not considered menstruation? Is the ghusl of one who achieves purity by dryness valid if she previously saw yellow discharge and then became dry?

Purity is achieved by one of two signs: complete dryness or the white discharge. If a woman sees either of these, she must perform ghusl immediately. If bleeding, even a little, resumes and it is within her usual menstrual period, she is considered to be menstruating again. If she sees a yellow or brownish discharge after achieving purity, then if it is within her menstrual period, it is considered menstruation; if it is outside her menstrual period, it is not considered menstruation. However, yellow or brownish discharge connected to blood is always considered menstruation. If a woman delays ghusl beyond its obligatory time after seeing the sign of purity, she must make up the missed prayers. The same ruling applies to your sister.