Is it permissible to perform a precautionary ghusl after menstruation due to the fear that the bleeding might not have completely stopped at the time of the first ghusl?

It is not prescribed to perform ghusl (ritual bathing) after menstruation except after verifying its cessation by seeing one of the two signs of purity: dryness (al-jufūf) or the white discharge (al-qaṣṣah al-bayḍā’). If there is doubt about purity, the default is that menstruation is still present. If she performs ghusl after verifying purity, it is not prescribed to repeat the ghusl out of caution, lest the door to obsessive doubts (waswasah) be opened. We advise against performing ghusl until purity is verified and against repeating ghusl thereafter.