Is it permissible for the wife's father to deduct from his daughter's inheritance to cover the deferred dower (sadaq) that the husband's family did not pay, with the knowledge and approval of the other heirs, but without the daughter's knowledge?

If the aunt guaranteed the money, she is obligated to pay it. It is permissible to take it from her without her consent if she refuses, otherwise, she is not to be demanded with it. As for writing a will for the husband, if it is from one-third of the wealth, it is valid. If it is from the daughter's share, it is not binding. If a man gifts each of his children according to their share, and they possess it, but he reduced his daughter's dowry, that is correct and must be executed.