This is extremely common among rescues and rehomed dogs. I'll explain first what I have come to believe this is, after I've observed various forms of this behavior in many rescues, and since I've sort of felt out what alleviates it best.
Dogs, I think, have a rudimentary sense of self, but only in relation to the ordered unit to which they belong. Who they are, in other words, is based on their place in the family - what is allowed, the routine, what they are expected to do. Dogs are
highly adaptable (Lassie Come Home is a bit of a myth) - but sometimes we kind of overdo it in our attempts to help them feel comfortable and "feel the love" we have to offer.
Your dog has no idea why she lost her last "pack". Until your dog knows her place, she's going to be terrified that anything she does, might lose
this home for her, also. She doesn't know how to interpret your actions. That's the fear you see.
For her, it's like it would be for you, if you mysteriously woke up in a strange hotel in a foreign country. You are wearing a uniform you don't recognise. People say things to you in Tagalog in a friendly tone - some of the words sound vaguely familiar but the context is wrong - and what are you supposed to be doing, anyway? Why are you there and where is your old family?
You notice everyone here wears guns - scary, how are you supposed to know who the good guys are and how not to cross them? Are you a bellboy, a guest, a soldier, a doorman, a waiter? Where are you supposed to be, what is your job? People are saying things in a more insistent voice, now pleading, now sternly, gesturing wildly (but the gestures are meaningless). No one is drawing a gun but the situation seems more tense all the time.
You might think of trying to hide until you could sort it all out, wouldn't you? I would! At the very least, you make appeasement gestures - you smile, shrug, shake your head, offer upturned hands - but they don't understand and your gestures seem to upset them in some way. Ooops, did you accidentally use an obscene or vulgar gesture? The more you appease and try to back away to get into a place where you can quietly watch and learn for a while, the more upset and frustrated they get. But these people keep insisting on drawing you into their frightening and strange world.
We have the advantage over dogs, of course, of higher cognitive powers - it might take us only a few minutes of quiet observation to figure out what people similiarly dressed, were doing. And language would quickly help us bridge the gaps within a few days - even if we had a learning curve to overcome. Remember how handicapped your dog is in that respect.
What a dog needs in a new environment is, in this order:
Routine: I have to jot it down for each newcomer, as my own household is quiet chaos at best. Do whatever is needed, to help your dog understand what happens in what order. Use a crate or quiet space to clearly define segments of time. You won't have to do this forever, just until you see her confidence return (no more than two months for the
most extreme cases). Quiet time also short circuits another problem seen during this time, with this type of dog - seperation anxiety. She'll learn she can be alone and it's just part of the routine. Incorporate feeding, training (very short easy sessions at first), quiet time, walks, and yes, even potty time. For a couple weeks I wouldn't even give her loose time in the yard - she needs to spend that time with you and your family members, or in quiet time.
Consistency: Define your rules and stick to them. If she's a really good dog and you don't actually need rules (I understand, that does happen) - make up a couple - sit before eating, come when called
every time. That coming when called thing could become problematic for you. Never coax, plead, sweet talk, or coo - just say, "Oh well!" and walk away. Obviously never let her offleash until you have the recall solid again. Get some expert advice on retraining that recall - book, or on here. Be positive but firm with her. If you are having trouble, say, putting her in the crate because she won't come, have her drag a leash so the recall is a non-issue. Get a cheap one at the dollar store and cut the loop so it doesn't snag something, though. [

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Affection: Yes, it's important, but it's last. And you'll show your affection in a special, dog-oriented way - by giving her a job to do! Start with something easy - a walk to your mailbox or to pick up your paper in the morning (she just comes with you - she doesn't have to pick up the paper yet!). Think of two or three things and incorporate them into your routine. During this time, her job is just to come with you, behave (you might think of more "rules" during these times!), and listen to you talk quietly - don't coo and babytalk, and if you don't feel like talking, or think she's too disturbed by it, that's fine too.
Make respect for her communication style as a dog, part of the affection you offer, too. We are primates and like to cuddle and hug chest to chest. Dogs, if they are VERY affectionate, like to gently touch side to side. I give in to my primate urges on my older dogs that know me, but on new dogs or puppies, I try to restrict myself to motherlike stroking - ears, neck, face, chest (male dogs go ga-ga for chest rubs - if you don't know why, go ask your mother [

] ), and side and back on a very confident dog.
A dog will come to you more readily if you back up and turn to the side - it's more inviting. They'll be more inclined to "sit" if you lean back on your heels rather than push your body forward as you give the command. We humans are bad ones for backing up our commands with wishful thinking body language - we want to "make" what's right happen. [

] Our children understand this body language as they are tuned to shaping and mimicry. Our dogs just see intimidating body language accompanying the verbal command - and dogs prioritize body language. If you open up into a more canine neutral position the dog will think more about the verbal command. This is especially true of the little dogs.
Whew. I totally didn't mean to write all that. But rehabbing this type of dog was my particular specialty in organized rescue so this topic is near and dear to my heart. Patience and consistency are key, of course - be VERY patient - it can take a couple months for normalcy to return, and it can take some dogs a year to really settle in. But you can help her settle in much faster with the above approach.