Is it permissible for the wife to dispose of her husband's money that he leaves with her without his knowledge, and is what she gave from it to her mother considered a debt upon the mother that necessitates repayment by the heirs?

What the husband gives to his wife in terms of money, if it is for household expenses (nafaqa), then she is an agent concerning it, and it is a trust (amana) that she may not dispose of except in what the husband has specified, with the exception of giving a small amount in charity, which is customarily permitted. However, if the money is given to her as personal spending money, then it is her property to dispose of as she wishes without her husband's permission, and she may give from it to her mother. In the first case, the wife guarantees the money she gave to her mother and is obligated to repay it to her husband.