Answered by Shaykh Rami Nsour
Question: According to the Maliki Madhab, during Ramadan, if a female believes she is at the end of her monthly menses can she take ghusl and make intention to fast prior to fajr? What does she do if she still has her menses after waking up later in the day, if she has made intention to fast?
Answer: A woman on her menses is only required to check before she goes to sleep. She does not have to wake up at the end of the night to check before fajr and actually to do so is disliked. If she happens to wake up before fajr and find that her menses are over, then she must make the intention to fast that day.
As long as the menses are still present, then a woman may not take a full shower (ghusl) with the intention of purifying from the menses. She must wait until the menses are fully gone before taking a full shower (ghusl).
In terms of fasting, an intention to fast while the menses are still there is not valid. The menses must have stopped before fajr for a woman to intend to fast that day. If it stops before fajr and she knows that, then she can make an intention to fast even if the full shower (ghusl) is done after fajr.
If one has to take a shower after fajr, they should be very careful not to swallow any water. The person must also be careful to not breath in the steam of hot water because that will break the fast.
[Dusuqi, Hashiytaul Sahrh al-Kabir]