Is the questioner considered to be severing ties of kinship, and what should she do regarding her maternal uncles who are boycotting her mother over inheritance and refusing to visit them, while she continues to communicate with some of the daughters and wives of her maternal uncles on occasions?

You are not severing ties with your kin or mistreating them if they are the ones who initiated the severance and mistreatment. Rather, you are performing a great good by maintaining ties with them. Maintaining ties of kinship is achieved through visiting, calling, corresponding, greeting, and anything customarily considered a connection. Among the greatest forms of maintaining ties is enjoining them to good and forbidding them from evil, and inviting them to repent from injustice and consuming wealth unlawfully. If they do not repent, there is no blame in boycotting and abandoning them after informing them of the reason for the abandonment.