Segregation rules for females studying in Saudi Arabia
I myself study as a PhD student in King Abdullah University of Science and Technology (KAUST). It's a mixed-gender university. A single woman can study here without being accompanied by a husband.

It is a graduate-level university, that is, you can study only for Master of Science (MSc) or Philosophy Doctor (PhD) degrees here.

Regarding programs we have applied mathematics, computer science, electrical engineering, material science, Earth science, marine science, environmental science, statistics, mechanical engineering, chemistry, and many others (I'm not aware of all possible fields that are studied here).

You can find more information on the official website (https://www.kaust.edu.sa/en).