Is blood that comes after eight days from performing ghusl following menstruation considered menstrual blood or istihada (non-menstrual vaginal bleeding)?

This returning blood is not considered menses, due to not reaching the minimum period of purity between two menstrual cycles, and because its total duration, combined with the previous blood and the period of purity between them, exceeds fifteen days (the maximum duration of menses). Therefore, this woman is in a state of istihada (non-menstrual bleeding) and must perform what a woman in istihada performs.