Indeed she is. One of my favorite Queen's Blade characters. She doesn't seem as popular as some of the others, but I find her rather intriguing and I like her design.
Ntx, Airi and Alleyne are easily the most attractive girls in the series. Airi gets more attention because of meido appeal, and I don't see why not many people like Nyx. Maybe because of her psycho nature in the books, and loser status in the manga...
In the anime, she's just a sore loser. She was a weak, pathetic slave who wanted power. She finally got that power, but it was pretty much borrowing from the staff and she didn't deserve it. Although she claims to fulfill "Justice," she made a deal with a demon, selling her soul and body. She also doesn't carry "Justice" on as she sometimes just burn a whole village down instead of saving people. Also, I think she is probably the weakest will/mind power for any characters in anime history. She can't do anything without her staff, and freaks the fuck out whenever she sees anyone "scary." No wonder her staff punishes her so often, she's such a fucking disappointment to him. She is even a dumb shit as she just lets go of the staff because she was taunted to do so. Of course, this ends to her humiliating defeat as she forfeits even without trying to fight. She was clearly just created for tentacle rape fetishes.