What is the ruling on the prayer of a married woman who has not menstruated for two months and from whom brown discharge is intermittently expelled? And must she wait until she sees complete purity?

If the brown discharge appears after fifteen days of purity and lasts for a day and a night or more, it is considered menstruation (hayd), and she should abstain from prayer and everything else that is unlawful for a menstruating woman. If it continues for the usual duration of her period and then stops, she should cease [abstaining], perform ghusl (ritual bath), and pray. If it continues for longer than her usual period but does not exceed fifteen days, some scholars (like the Shafi'is) consider all of it to be hayd, while others (like the Hanbalis) consider the excess to be purity until it recurs three times, at which point all of it is then considered hayd. If it continues for more than fifteen days, she is considered to be suffering from irregular bleeding (istihada). In this case, the days of her usual period are considered hayd, and anything beyond that is istihada, for which she does not abandon prayer or fasting. A woman with istihada should perform ablution (wudu') for each prayer after its time has begun, perform istinja' (cleansing), and tie a cloth to prevent the discharge of impurities.