What should a woman over fifty do if she did not make up for the days she missed in Ramadan due to menstruation previously, being unaware of the obligation to do so, but has now learned of its obligation?

She must make up for those days, and it is more cautious for her to feed a poor person for each day.

She must seek Allah's forgiveness and repent to Him, fast the days she missed, and feed a poor person for each day (half a Sa' which is 1.5 kilograms) if she is able; otherwise, the feeding is waived. If the second Ramadan comes before she makes up the days, she has sinned. If she does not know the number of days, she should act based on her best estimate and fast the days she believes she missed. She must repent to Allah for not asking people of knowledge, and she must make up the fasts and expiate for each day by feeding a poor person if she is able.