Is a wife's fast valid if her post-natal bleeding stopped at night and returned during the day, bearing in mind that she used to perform ghusl every day?

The jurists have agreed that there is no minimum limit for postnatal bleeding (nifas), and that if a woman sees purity, she should perform ghusl and becomes pure. They differed on its maximum duration, and the preponderant opinion is forty days. If a woman becomes pure within this period and then the bleeding returns: - If it returns before fifteen days, then the blood is nifas, and there is a difference of opinion regarding the intervening purity (al-talfiq and al-sahb). - If it returns after fifteen days or more (the minimum period of purity), and the bleeding continues for a day and a night or more, there are two opinions: either it is menstruation (and the purity is actual purity), or it is nifas (because it occurred during its possible time).

Based on this, the blood the questioner sees at night and stops during the day is nifas blood because the period of purity has not reached fifteen days. Regarding the purity within it, there are the two opinions of al-talfiq and al-sahb. Thus, her fasting and prayer are valid according to the opinion of al-talfiq, and not valid according to the other opinion. She may adopt either of them.