Is the bleeding that a woman experienced for a day and a half and then stopped, after she used birth control pills, considered استِحاضَة (non-menstrual vaginal bleeding) as the doctor said?

If the blood a woman sees occurs at a time suitable for menstruation, and fifteen days or more have passed since the cessation of the previous menses, then it is a new menstruation. If the time between seeing this blood and the previous menses is less than fifteen days, and it is possible to consider it, along with what preceded it, as a single menstruation (such that the total of the two blood flows and the period of purity between them does not exceed fifteen days), then it is considered a continuation of the previous menstruation. This is the view of the Shafi’is and some Hanbalis. However, if the blood occurs at a time unsuitable for menstruation (for instance, if the total of the two blood flows and the period of purity between them exceeds fifteen days, and the duration between the two blood flows was less than fifteen days), then it is Istihada (non-menstrual bleeding).