How can a woman help her needy relative who lives in another city, if sending money to her might expose it to usurpation by her delinquent sons, and the woman is unable to travel to her due to the unavailability of a mahram?

May Allah reward you for your care for your relatives and for not traveling without your mahram. Maintaining ties of kinship is one of the best acts of righteousness. The Prophet (peace be upon him) said: "Whoever wishes that his provision be expanded for him and his life span be extended, let him maintain ties of kinship." And charity given to relatives is both a tie of kinship and an act of charity. Therefore, spare no effort in helping them and extending a hand of assistance with the items they need. You can also entrust some money to a reliable person to spend on them, ensuring it does not fall into the hands of their foolish children or similar individuals, thereby safeguarding your money and guaranteeing it reaches your relatives.