All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The scholars have agreed that a woman in menstruation when she becomes pure from her menses during the day in Ramadan, she has to make up for this day; the same applies to women in their confinement period. However, they differed as regards whether she should refrain from eating the remainder of that day. There are two different opinions about this. The most correct one is that she does not have to fast the remainder of that day and she can eat and drink. This is the view point of Imaam Maalik, Shaafi'ee and Imaam Ahmad and others . It is reported that Ibn Mas'ood said: "Whoever had eaten at the beginning of the day, he is allowed to eat the remainder of that day." Therefore, the sister asking the question does not have to fast the remainder of that day, but she has to make it up another day.
Allaah knows best.