An alleged female on the internet who intentionally posts pictures of her scantily clad self, types sexual innuendo on message boards, and otherwise openly flaunts the fact that yes, she is a female, on the internet. All this is done to gain popularity on forums and to attract attention.
The nerd hag often uses more than her fair share of smiley faces.
Also see: Attention Whore
They are sirens of the intarwebs, tie yourself to the mast.
In the middle of a discussion:
Forumer: As I was saying, blah blah blah you've contradicted yourself
Nerd Hag: :)1 sec my bra came loose brb :) *blushes*