What should a woman do who missed a large number of days of Ramadan fasting due to migraine and was unable to make them up because she did not know the exact number, knowing that she fasted and gave charity with the intention of making up and expiation?

There is no sin upon you for breaking your fast on the days you were ill or menstruating, but you must hasten to make up those days. Charity and supererogatory acts do not substitute for making up the fasts; you are obligated to make up what you missed. If you are unable to ascertain the number of days, then investigate and make up what you believe, most likely, absolves your responsibility, as Allah Almighty says: "So fear Allah as much as you are able." If you delay making up the fasts without a valid excuse until another Ramadan begins, then you must make them up along with feeding a poor person for each day. If you have made up some days and believe that you have made up what was due upon you, then this is sufficient. Otherwise, continue making up the fasts until you are reasonably certain that your responsibility has been absolved.