This NPC was removed in the 4.0.3a "The Shattering" patch prior to Cataclysm's release, and she no longer exists in game.
I accidentally bumped into her on my warrior when I was level 60 (just rushed her without paying attention to the fact that she had a unique name), and she destroyed me. I had to drag a priest friend out there to help me kill her. She has a Shadow Word: Pain DoT, VERY hard melee, and a mind control she'd use if you had anyone else with you. Even with my priest friend there, it took us a couple of tries to take her down just because that mind control kept messing us up.
Леди Хедерина
