What is the ruling on what the questioner did by relaying her sisters' offensive words about their mother to the mother, and what is the ruling on the sisters' words about their mother, and should the questioner have remained silent?

Parents hold a great status, and it is obligatory to honor them, especially the mother, who endured and persevered. Filial piety towards the mother does not cease even if she errs or wrongs, rather it is ignoble to respond to her kindness with ill-treatment.

Gathering to abuse the mother and backbite about her is a grave act of disobedience (uquq adheem). The children should strive to mend the relationship between the sisters and the mother through gentle consultation, supplication (dua), and seeking help from someone influential, because reconciling disputes (islah dhat al-bayn) is a great good.