Yeah, my antagonist did the same thing, and she's even still constantly evolving. Like, when I brainstormed the society and their rules, I discovered her motivation and why the MC is such a threat to her. She was never intended to be the antagonist and she was only going to have a small bit part in the story, but then she showed me her colors and I couldn't help but put her in.

I feel like I have a much better grasp on the story, however it is far from the one I started with. I don't even recognize the original idea in the notes I have (and there's a ton of them!). Maybe this is why I've had such a tough time with outlining.

And can I just say how nice it is to have a place to come to talk about all of this!