Does a married woman's refusal to host her sister in her home—due to the sister's harming her and stealing her privacy—constitute disobedience to her parents if this prevents them from visiting her, and is she thereby severing ties of kinship?

Our advice to you is to be patient with your sister's harshness and bad treatment, and to treat her kindly, in accordance with the Hadith of Abu Hurairah: "If you are as you say, then it is as if you are feeding them hot ashes, and there will always be a supporter from Allah with you against them as long as you remain in that state." Your patience with her and your kind treatment of her will please your parents, whose dutifulness Allah has made obligatory. If reconciliation is achieved, you will have the reward of patience and maintaining kinship ties. If kind treatment does not benefit, then you are not contributing to the severing of kinship ties.