Is reminding one's mother of the help provided to a brother, due to her not acknowledging it and asking for more, considered an act of "minn" that invalidates the reward?

One should not argue or raise one's voice at one's mother, for her intention is to emphasize and urge. It is obligatory to be humble and dutiful towards her, due to the Almighty's saying: "And your Lord has decreed that you worship none but Him. And to parents, show goodness. If one of them or both of them attain old age with you, say not to them a word of disrespect, nor repel them, but address them in terms of honor. And lower to them the wing of humility out of mercy and say, 'My Lord, have mercy upon them as they brought me up when I was small.'" And due to the Prophet's, peace and blessings be upon him, saying: "Your mother, then your mother, then your mother, then your father."