How can one deal with negative feelings towards a sister who accused her father of injustice and of causing her mother's death, while still desiring to maintain kinship ties and family cohesion?

The mother's right after her death is that one supplicates for her. The presence of a father is an invaluable blessing and opportunity. God has commanded to treat him with kindness, especially in old age. One should excuse the father for marrying and assist him in it, as an elderly man is more in need of a wife to care for him. One must strive for what unites hearts and strengthens brotherhood, and advise the wrongdoer and warn him against disobedience to parents. The woman who speaks ill of her mother should be advised to supplicate and seek forgiveness for her instead of judging her.