The Queen in Red is a dangerous woman, always dressed in red, who has appeared many times in history and art, often at times of great bloodshed and tragedy. Destruction and pain are sown in her wake.
The Queen in Red makes a wonderful villain or plot device character in the World of Darkness. There are several options.
The Queen in Red was originally a creation of the Cthulhu mythos. In Call of Cthulhu she is an avatar of Nyarlathotep. While the relationship has never fully be defined she is often thought of as a companion of the King in Yellow.
The Queen may be an ancient demon.Her modus operandi and apparent immortality lends credence to this theory.
If you don't want to take the demon route, she could be a Maeljin that came into existence after the murder of Father Wolf. Perhaps she's even Lilith, herself.
The final option (and the one that I think I will use in my games) is that the Queen in Red is Bloody Mary, the companion of Bloody Jack. These powerful entities are described in Vampire: The Requiem Mythologies. They inhabit some sort of spirit dimension and can access the mortal world through mirrors. They are known to make bargains with kindred, teaching them the rare and strange discipline of Ars Speculorum (Art of Mirrors).