Thanks for the suggestions everyone. I know I have a lot of work ahead of me, but she is definitely worth it. I'd do anything for my best friend!
Oh! I think we're having some progress with her. My neighbor's granddaughter is staying the week. The first few days Pippin would bark at her anytime she got near the fence. I had the girl just sit at the fence and I would treat Pip every time she looked at the girl or walked near the fence. Eventually I had Pip eating treats out of her hand!!! (I told the girl not to try to give her treats or pet her unless I'm outside, of course. Just in case Pippin would get spooked.) But I'm super excited about this progress!