Must one make up for the three days during which menstruation stopped at an unusual time, followed by confirmed purification and ghusl?

A woman must initiate ghusl immediately upon seeing the sign of purity (cessation of menses), and it is not permissible for her to delay. If you waited this period without performing ghusl, you have erred. You must make up the prayers you missed during that period, as they are a debt upon you.