My wife intended to fast the whole month of Rajab, without thinking about her period. Now her period has arrived, and she realized that she will not be able to fast the whole month. Does she have to make up for these days?
To make an intention to fast the whole month of Rajab does not make fasting
in Rajab compulsory.
If your wife did not fast during her monthly cycle, she does not have to
make Qadhaa (make up) for those days.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai