Thank you both. People here have been telling me for over a month to break up with her. I tried to give it as much time as possible, but I guess I always knew it would come down to this. It had to.
She will absolutely try to manipulate me with the old standbys: she has nowhere to go, what about her job, she always knew I'd leave her because of her illnesses, etc. But it's time, and she had too many chances already.
Thank you all for your support. I will keep you updated.