What is the ruling on a sister working and residing in student housing, knowing that the majority of the students are expatriates and do not have a mahram, and does the hadith apply to her: "May Allah curse the woman who takes off her clothes in other than her husband's house"?

There is no harm for your sister in working at the student dormitory, and it is permissible for her to reside there without a mahram. However, she should not travel to or from it except with a mahram. As for the hadith, "No woman removes her clothes in other than her home except that she severs what is between her and Allah the Almighty," it refers to removing clothes in front of non-mahram men in public places, not in safe places. She should also invite to good, enjoin what is right, forbid what is wrong, and strive for reconciliation.