Is a woman sinful if she delays making up an obligatory fast?

The answer varies depending on what you mean by "debt" (دين - dayn):

1. If you mean missed prayers: The preponderant opinion is that it is obligatory to make up missed prayers immediately and in order, unless doing so would harm one's livelihood or body. Whoever delays making them up without an excuse is sinful. 2. If you mean making up missed fasts: The majority of jurists hold that making up missed Ramadan fasts can be done at leisure between the two Ramadans, but it is recommended to hasten in order to clear one's conscience. It is obligatory to make up the fasts immediately and consecutively if there is only enough time left before the next Ramadan to cover the number of days to be made up. Whoever delays making up the fasts without an excuse until the next Ramadan begins is sinful, and it is obligatory for them to make them up and to pay expiation by feeding one poor person for each day. One who has an excuse is neither sinful nor subject to expiation. 3. If you mean a loan (financial debt): If you are in financial hardship: There is no sin upon you, and the creditor cannot demand immediate payment, but you must strive to repay. If you are able to repay: If the creditor demands repayment: You are sinful if you do not pay immediately. If the creditor does not demand repayment: Scholars differ, but the most cautious approach is to pay immediately to avoid disagreement.