Is it obligatory for a woman to perform ghusl upon the cessation of the brown discharge that immediately follows menstruation, or upon seeing the white discharge? And is she required to make up the Isha and Maghrib prayers if she performs ghusl before Fajr?

If a woman sees purity by one of its two signs, dryness or the white discharge (al-qassah al-bayda'), then the ruling of menstruation is lifted from her, and ritual bathing (ghusl) and prayer become obligatory for her. She is not required to wait for the other sign. The preponderant opinion is that she performs ghusl as soon as she sees purity. If she becomes pure before Fajr, then Maghrib and Isha prayers become obligatory for her. If she becomes pure before Maghrib, then Dhuhr and Asr prayers become obligatory for her, according to the majority of scholars.