What is the ruling on the prayer and fasting of a woman who used to be shy about performing a full ghusl after menstruation, so she sufficed with letting water reach her scalp without washing her hair completely, fearing that someone might see her hair wet?

Menstruation is a natural phenomenon; it does not justify falling into what Allah has forbidden, and laxity in purification because of it is not praiseworthy modesty but rather weakness and evil. If water did not reach all of the hair on the head during the ritual bath (ghusl) after menstruation, then the prayers performed after this incomplete ghusl are invalid and must be made up, along with repentance and remorse, if the woman knew that it was obligatory to wash all of her hair. However, if she was ignorant of the obligation to wash all of her hair, or thought that what she did was sufficient, or that her modesty was an excuse, then she is not required to make up the prayers that were missed after their time had passed.