I rescued a dog like this...
It takes lots of time and alot of counter conditioning to get them to come around...
Does the dog live inside? Does she have a crate?
How are you teaching the dog? Are you using
PR only or a mixture?
These types can shutdown from the tiniest trigger. They respond only to
PR and any aversive kills them inside.
I would break out the high value treats and move SLLLLLOOOWWW....lol Even praise can shut a dog like this down if it scares her.
Just simple and quiet commands and TONS of food.