Ghost Hag was the name for the person who was sacrificed for the Snowy Night Village and was then turned into a 'Ghost Hag' by the God of the Snowy Night Village. The only Snowy Night Villager who escaped from being turned into a ghost hag during the sacrificial ceremony was Asagiri. They appear during Asagiri's flashback.
Ghost Hags, in a logical sense, would vary from appearances. However they are mainly shown wearing a messy, single-colored and tattered Yukata. They appear to be weary and old, with black voids containing their eye sockets, and only having a few strands of hair atop their almost bald head.
Since they are the previous sacrifices, and all of the sacrifices have been confirmed to be female, it is reasonable to come to the conclusion that all Ghost Hags are female.