Welcome to YT!
Praises to you for helping an abused dog! You have already received some good advice.
I'm wondering if you have changed her diet/dog food? That may account for the loose stools.
Her nervous behavior probably isn't helping her stomach either.
If she was abused, her vet care may also have been neglected. I would make sure she is up to date on shots, etc. and have your vet check her over like he might check a new puppy.
best wishes!
yorkiesmiles