Is money earned from working at a Coptic association, and providing services to them as a Muslim woman, considered unlawful gain?

If the work at the association does not involve anything religiously forbidden, such as printing religious books or participating in missionary activities, and does not aid in disbelief (kufr) or polytheism (shirk), then there is no harm in it, and the earnings are lawful. It is permissible for a Muslim to work for a Dhimmi (non-Muslim living under Muslim rule) provided that the work is permissible. Personal service is an exception according to some scholars, such as the Hanbalis, out of concern for humiliating the Muslim. However, other works, such as sewing a garment or specific tasks for a known period, are permissible.