What should a 47-year-old daughter do, who works on temporary contracts and spends on her elderly parents and the household, while her well-off brother contributes very little to the expenses, which causes tension and problems in the family?

If the father's salary is insufficient for his and the mother's expenses, then it is obligatory upon the children to spend on them in a reasonable manner. This expenditure is distributed among the children according to their financial capability (wealth), not equally, nor according to the inheritance share. So, if a brother is in a better financial situation, then he is obligated to bear a larger portion of the expenditure. If the brother does not respond, then the questioner must spend on her parents in a reasonable manner, as long as she is able to do so without incurring harm to herself, while seeking reward from Allah, for showing kindness to parents is among the causes of Allah's pleasure.