What is the ruling on the fast of one who purified after Dhuhr and did not intend to fast from the night?

It is impermissible for a menstruating woman and a woman in post-natal bleeding (nifas) to fast, by scholarly consensus. They are obligated to make up the days they missed after Ramadan. If a menstruating woman purifies herself after Fajr (dawn), her fast for that day is not valid and she must make it up. Scholars differed regarding the obligation of refraining from eating and drinking for the rest of the day, but the more preponderant opinion is that she is not obligated to refrain.