Is it considered an act of disobedience if the mother rejects the dowry that her daughter accepted from her husband?

Your mother or guardians do not have the right to prevent you from accepting the agreed-upon dowry, as long as you are of sound mind. If a woman agrees to marry for a dowry less than that of her peers, her guardians have no right to object or prevent it. Otherwise, the one preventing her becomes an 'adil (one who prevents marriage), and the ruler will marry her off. Your acceptance of the dowry is not an act of disobedience towards your mother, but you must still be dutiful and kind to her and seek to please her.