Hornet is sometimes referred to by others as Gendered Child. Why is that? There are enough female bugs in the world for it not to be that rare.
Warning: Spoilers ahead. Feel free to read at your own risk.
Hornet is made from the Void, just like the main character and the other Vessels. However unlike the Vessels, Hornet was made at request from Herrah the Beast in exchange for Herrah becoming a dreamer. While the exact circumstances of her creation are not clearly defined, both the White Lady and Herrah herself, consider Hornet to be their daughter.
The specific naming of “Gendered Child” sterns from the fact that Vessels canonically have no gender, due to the fact that they are empty shells only designed to hold the infection. Given Hornet is also made from the Void, this makes her the only creation from the Void to canonically have a gender. (The kingsmoulds are simple automatons and the Collector is ambiguous enough in both voice and behavior).