What is the ruling on fasting and prayer for a woman who sees very light red blood, without an odor, and only sees a single drop per day, after her menstrual period has been absent for three months?

The minimum duration for menstruation considered legally valid is one day and one night according to the Hanbalis and Shafi'is, and three days and nights according to the Hanafis, and a single drop according to the Malikis. If a woman finds only one drop of blood each day with complete dryness otherwise, then what she finds is not menstruation, and she is obligated to pray and fast. This drop is impure, and she must cleanse herself from it, and it nullifies ablution.