Is it permissible for a woman who vowed to give food to neighbors and the poor, and is elderly and wishes to make things easier for herself, to substitute that by buying carpets for a mosque, knowing that the cost of the carpets will be higher?

A vow must be fulfilled whenever a person vows an act of worship or an act of devotion, for Allah, the Almighty, says: "And let them fulfill their vows," and the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him." Allah has praised those who fulfill their covenants and condemned those who break their promises. If the one who made the vow specifies a particular recipient for their vow, it must be disbursed to them. Therefore, the woman mentioned in the question must distribute the food to the neighbors and the needy as she vowed. It is permissible for her to appoint someone to prepare the food on her behalf, even for a wage.