What is the ruling on a female teacher receiving her salary during the summer, despite the absence of students and her not being assigned any work, knowing that this occurs without the Ministry's knowledge? And what should she do if the salary is unlawful?

If the school administration is authorized by the Ministry of Education to exempt you from summer attendance, then your salary is lawful. However, if they are not authorized, it is not permissible for you to take payment for the period you were absent, and it must be returned to the Ministry, unless the authorized entity forgives you. This is based on the Almighty's saying: "O you who have believed, fulfill [all] contracts," and the Prophet's (peace be upon him) saying: "Muslims are bound by their conditions."