What is the ruling regarding the stay of the husband's nieces in his house for two months, and what is the ruling regarding the husband giving his wife the choice between enduring hardship or severing ties of kinship on the pretext of helping those in need? Is the wife wrong in this?

Your objection to your husband's nieces staying in your home for two months or more, without a separate section with its own facilities, is not wrong, due to the discomfort it causes the wife, and because an independent dwelling is a right of the wife. The husband should not restrict his wife in this regard or impose upon her what the Sharia does not oblige her to do. However, it might be better for you to be patient and tolerate their stay as long as the period is limited, and there is a benefit for you in it, which is the girls staying with your children in your absence. Your approval will improve the relationship between you and your husband and his in-laws, and it will close the door to Satan.