Is the daughter sinful for informing her father of her mother's desire to demolish a wall in his absence, and will the mother's supplication against her daughter because of this be answered?

It is not permissible for your mother to demolish a wall of the house owned by your father without his permission. You must prevent her from doing so by informing your father, as this falls under preventing aggression against others' property. A mother's supplication will not be answered if it is unjust, because she would then be an oppressor and a sinner. One who supplicates for sin will not have their prayer answered, as stated in the Hadith: "The supplication of a servant continues to be answered as long as he does not pray for sin or for the severance of kinship ties."