I completely agree. Billy mentions that she was happiest when the Natives worshiped and feared her. I mean, she was abandoned at birth, and grew up on her own. Though it is hard for us to imagine, she has never been loved, or has had anything to love in return.
It's sad, when you think about it. That's why she wants to rule, because she wants to feel like she's wanted, and needed. I think she's just terribly lonely. I can see why - imagine being on your own, for all that time, and never knowing any different, and then, seeing love first hand, see what you're missing out on, and know that you'll never have that.