There is only one harpy queen in 'The Witcher 2: Assassins of Kings. She is found in the harpy lair. She is surrounded by "attendant" Celaeno harpies and can cause bleeding, so beware. Once defeated, she drops a sword named "Harpy".
Associated quests
Video
The Witcher 2 Assassin of KIngs Harpy Queen Battle (Insane)