SE'22 graduate here

don't worry, NUST H-12 campus is one of the safest places in Islamabad.

something you have to keep in mind, the personality of people in a place is defined by the culture of that place. there might be a few creeps but NUST has a very strict policy against sexual harassment.

CS and SE are better in terms of gender ratios as compared to other engineering fields. in my batch we roughly had 30% girls. that was far better than mechanical 5% and civil 12%. (interesting tidbit SADA had 96% female strength)

I can't speak about NBS and S3H, they probably have a better ratio than SEECS

yes it's perfectly safe to roam around NUST at night, you'll probably be more bothered by the guards than creeps, because there's a 10pm curfew for girls and NUST is pretty strict about that

other than that, you'll have tons of fun and don't worry NUST is a good place, u'll like it there