How can God be pleased, and what are the duties incumbent upon the female questioner towards her siblings and mother, and is returning mistreatment to the stepfather forbidden?

It is obligatory to be dutiful to one's parents and to treat them with kindness, as this brings good in this world and the Hereafter. It is not permissible to harm the mother, even if she harms her child, and one must be cautious of anything that displeases her. Retaliating evil with evil is permissible, but forgiveness and pardoning are more virtuous, especially if it leads to the mother's displeasure. There is no obligation to allow the stepfather to reside [with you], and it is better to try to persuade the mother for him to leave, to avoid disputes, and to seek assistance from righteous and wise people for reconciliation. As for service in the house, it is obligatory to serve the mother in what she needs, as long as it does not cause harm or unbearable hardship. The mother's right to custody is forfeited if she marries another man.