What is the ruling on one who broke her fast in Ramadan, thinking she had not yet become pure from menstruation, then it became clear to her that she was pure: is it obligatory for her to only make up the missed days (qada') or to make up the missed days and offer expiation (kaffarah)?

Among the conditions for the validity of fasting are forming the intention [for it] at night and a woman's purification from menstruation before Fajr. If a woman does not know of her purification before Fajr but realizes it after, she must make up that day because the intention was not formed at night. There is no sin or expiation upon her because she did not intentionally break her fast. She must, however, refrain from eating and drinking for the rest of the day. But if she was intentional, she is sinful and must make up the day without expiation, according to the majority of scholars, while some have deemed expiation obligatory.