The Graceful Fairy Venoms are an offshoot of the Mao Shan Ghosts. Or possibly a renegade splinter faction, or perhaps even just a group of young recruits just killing time (and people) while waiting for orders.
The fact of the matter is, three young ladies by the names of Ghost Wind Flute, Divine Venom, and Hidden Corpse-Sword were recently recruited by the Mao Shan Ghosts clan and trained by their leader. But that leader retired when he felt the recruits were skilled enough and nobody has stepped forward to fill the void he left behind. The girls don't seem to accept the orders of any of their peers as legitimate, even though they are their seniors, and so they find their own things to do. Maybe when the Mao Shan has a proper new leader they will fall back in line. Or maybe they will strike off on their own for good. But in the meantime they're a group of overeager and uncontrolled assassins, which has already resulted in a few unnecessary tragedies.
They also have a pet ferret which they name Ghost Face.
From top to bottom: Ghost Wind Flute, Divine Venom, Hidden Corpse-Sword, and Ghost Face.