What should I do and how should I act with my mother who pressures me for money and resents my marriage, given my difficult financial circumstances, my modest income, my rent, my expenses, and my spending on my daughter?

If your mother's treatment of you and your wife is poor, this is a tribulation, often motivated by jealousy. We advise you to be patient with her and to recognize the greatness of her right, for Allah has given her a special injunction, and the Prophet (peace be upon him) made her right to devotion three times greater than that of the father, due to the difficulty of her pregnancy, childbirth, and nursing. Among the best ways to show devotion to both parents is to frequently supplicate for their righteousness and guidance. Strive to give your mother from your wealth to earn her satisfaction; if she asks of you what would harm you, then appease her to avoid her anger.