I am so very sorry to hear that this is happening to your girl!
When they experience trauma, it can take a long time to desensitize them to these things, and some of them never truly go back to the way that they were.
Some things to consider:
It is very easy to re-enforce the unwanted behavior. Our temptation is to say, "It's OK, good girl." any time we see them afraid. Remember that you are re-enforcing the fearful behavior by praising her at those times.
It is important, though, to praise her when she is doing well. If she comes to you or the food bowl, and comes out of hiding, that is the time to lay on the praise!
If the Prednisone is not making any changes, I would talk with your veterinarian about stopping it. Unfortunately, Pred can be dangerous to stop abruptly, but it can worsen paranoia in humans, so it only makes sense that it may be feeding the fear in her as well.
There are medications that can help with training and fear, such as Clomicalm and even doggy Prozac. Discuss these options with your veterinarian.
I hope this helps!
As always, if you have further questions or concerns, please don't hesitate to ask them using the "reply" function.