I know you took in both dogs, but maybe you should look at rehousing the shepherd with someone else. Hudson seems to be doing great, but your shep seems to be getting anxious about something.
I was told by a trainer when my female mal was attacking my other dog a shepxrotti to remove her from teh situation for 24 hours. He said to use the garage or shed, somehwere secure and safe for her to be, have water but no food in there, and put her in the place. When you get her out in 24 hours if she attacks the other dog, repeat the exercise.
I did not do this as i felt it was not the right thing for us but maybe this would help you.
She came from an abusive home, you know that, so please don;t hit her.
If you feel the need to, find her another home.