What is the ruling on shunning a sister due to a quarrel that occurred between the spouses, and what is the ruling on ordering the family to shun her and limiting interaction to only greeting her without speaking?

It is not permissible to boycott your sister or to order your family to boycott her because her husband mistreated you, as Allah Almighty says: (And no bearer of burdens will bear the burden of another). You must hasten to uphold ties of kinship to avoid being cut off by Allah, for in the noble Hadith: "Are you not pleased that I should keep ties with whoever keeps ties with you, and cut off whoever cuts ties with you?" And the one who upholds ties of kinship is not he who reciprocates, but rather he who maintains his kinship ties even when they are severed. It was incumbent upon the parents and siblings not to obey you in boycotting her, because there is no obedience to a creature in disobedience to the Creator; rather, they should have encouraged you not to boycott her.