Welcome! Thank you for saving her. It sounds like you have a good start! I would continue to work slow & steady w/ her. If she seems to improve then get worse just back up a step in training & start again. Maybe offer a really tasty treat (little pieces of leftover meats or freeze dried liver treats for dogs). Once she has overcome her fear of new surroundings & things then enroll in a puppy class for socialization & some basic obedience and then follow w/ a basic obedience class. Make sure it is w/ a reputable trainer, especially w/ her being timid.
Spend a lot of time w/ her but not TOO much as w/ her condition she might encounter seperation anxiety when you leave.
After her vaccines are given try to get her out often to get her used to new things.
What is her name? I love mutts! I have a couple that came from a shelter off death row & everyday I guess another breed that might be mixed in. It is a fun guessing game.