Congrats! And good for you for rescuing her. My parents dog is a rescue. Maybe not so much from a shelter, but a family friend couldn't keep him anymore, and a few other families had taken him in and returned him. We couldn't bare to let him stay there any longer without a loving family. We have had him since and that was 7.5 years ago.

I also have a smaller dog (I know that is no comparison to your dog) but as far as the nipping goes we would say no and snap our fingers every time he tried to nip. It helped a lot. I'm not sure if it would help with a larger dog, but maybe it would.

Good luck! And she is just precious!