What is incumbent upon one who did not make up for the days of menstruation in Ramadan for several years out of ignorance, then they accumulated upon her? And how does she calculate and divide the days? And is there expiation upon her?

You must make up for the days you missed fasting. The calculation is easy: if your period was regularly 8 days, then you owe 104 days of fasting. If your menstruation is irregular, refer to Fatwa no. 99750. As long as you are able to make up the fasts, it is obligatory for you, even if it involves some tolerable hardship. You can spread out the make-up days or delay them until winter if fasting long days is harmful to you. If you are unable to make up the fasts due to an illness from which recovery is expected, then wait for recovery, then make up all the days, and divide the days so that you finish before the next Ramadan. It is not permissible to delay making up the fasts until another Ramadan without an excuse. Whoever delays it must make it up and feed a poor person for each day. If you delay making it up due to an excuse, then there is nothing upon you. You are required to repent for delaying the make-up fasts after knowing their obligation, and you are required to pay the minor expiation (750 grams of food for each day) if you knew the impermissibility of delaying until the next Ramadan began. As for what was delayed before knowing the obligation of making up the fasts or the impermissibility of delaying, there is nothing upon you for it except making it up.