What is the ruling on a wife going out alone in a car at night from the university after Asr and returning at the time of Isha prayer without a mahram or companion?

A woman is permitted to drive her car within the city during the day or night for a permissible purpose, even if she is not accompanied by a mahram or other women, provided that she is safe and secure, that her going out does not lead to any mischief, and that her husband grants her permission if she is married.