What is the legal ruling regarding irregular menstruation, where it occurs every 14 days and lasts 7 or 8 days, with signs of menstruation appearing a week after purification?

The minimum period of purity (Tuhr) between two menstrual cycles is fifteen days, according to the majority of scholars. Scholars have differed regarding the ruling on the purity period interspersed within menstrual bleeding if it does not reach fifteen days, with two opinions:

The first: That it takes the ruling of menstruation (the "Sahb" school of thought), so the woman must make up for any fasting she performed during that period.

The second: That it takes the ruling of a valid purity (the "Talfiq" school of thought), so she is not required to make up for the fasting.

It is permissible for a woman to act upon either of the two schools of thought.