Nepalgal,

If you are a female and want to go out of the Airport in Delhi then my suggestion is: be very very careful while hiring a taxi or auto to go to the city, even in the day time.

There are many instances of foreign female tourists, Nepali girl or even Indian girls of being forced, taken to wrong places or killed. Better if you don't have someone to receive at night, if you have no idea about the city or if you are travelling alone then my suggestion "do not go to the city from the Delhi Airport at night".