All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
The issues of menstruation are ramified and complicated and therefore scholars past and present provided different relevant opinions and Fataawa in this regard, each according to the sound opinion from his point of view. Nevertheless, you should consult a trustworthy and religious scholar and then act according to his opinion. You should not ask more than one scholar about the same issue, for this causes you confusion and disturbance. Following the opinion of only one scholar will spare you all this.
As for the question, the brownish discharge which comes out immediately before and after the menstrual period for four days is considered menstruation and the relevant rulings are applied. If the brownish discharge exceeded the maximum period of menstruation which is fifteen days and she can distinguish the menstrual blood from others, she can act accordingly. Otherwise, she has to count her usual menstruation period.