I can understand why people could be weary of overpowered characters. But with male godmod protagonists with a huge ego, I love it when there are smart females to take the upper hand of them and play them down a bit. It's a fun kind of dynamics for me. I also like mysterious creepy folks and shady tricksters. So the reason why I guess they hate her is the same why I like her :D She's fun, and her knowing shit the Doctor doesn't and being snarky about it makes it better for me.