What is the ruling on one who misses the entire month of Ramadan due to post-partum bleeding (nifas), and how should these days be made up? Is it to be made up by fasting only, or by giving charity only, or by both? And must these days be made up before the advent of the next Ramadan, or can it be done throughout one's lifetime?

Whoever broke their fast in Ramadan (definition) due to a valid excuse must make up the missed days before the next Ramadan. There is no specific month required for making up these days, though it is recommended to do so in Sha'ban. There is no charity (sadaqah (definition)) or expiation (kaffarah (definition)) due from her. However, if she delays making up the days without a valid excuse until the next Ramadan begins, then she must make them up along with an expiation for the delay, which is feeding one poor person for each day.