What should I do regarding my mother’s refusal of my wearing the niqab currently, citing the court's decision to ban women wearing niqab from entering exams, and what is the ruling on covering most of the face with a mask in this situation?

There is no blame upon the sister who asked the question if she suffices, during her exams, with wearing a mask that covers most of her face. This is because scholars differ regarding the obligation for a woman to cover her face, and it is permissible to take advantage of this differing opinion when there is a need, such as the mother's insistence on removing the niqab to avoid being barred from entering the exam, especially since most of the face is still covered.