Is blood that appears a week after the cessation of menstruation considered menstrual blood that necessitates making up for the fast?

The default assumption for blood seen by a woman is that it is menstrual blood. It is only considered istihadah (non-menstrual bleeding) if it is seen at a time when it cannot possibly be menstruation. Blood that returns after a day or two following purity is considered menstrual if it occurs within the fifteen-day period, which is the maximum duration of menstruation. If it stops after a day or two, there is no issue. However, if the duration of the two bleeding periods, and the period of purity between them, exceeds fifteen days, then she is considered to have istihadah, and she must make up the days she fasted while she was menstruating.