Reguardless of what caused it - you now need tofocus all your energy and all her energy on fixing it!
I am going to assume that you have gone over all the factors of your household - loud noises - other animals - a certain room (my dogs hate linoleum) the reactio nsay a man with a hat on has etc. etc. and have reasonably eliminated a household trigger.
So I'd say start slow, start over infact. Like this is the first time you met her and all you know is she is scared to death. I'd suggest simply sitting in the middle of the living room on the floor and toss high value treats - cheese or cut up hot dog. Don't even worry about tossing them in her direction - just litter the room with them. Praise her, in a high pitched happy but not very loud voice. Just do this for a few days - or as long as it takes (even if it is weeks) to look to you to give her another piece - let her initiate the interaction - and then move on to hand feeding her.
I would hand feed her all her meals - litterally food in your fist going to her mouth slowly calmly with lots of positive reinforcement.
I would put something of yours that smells like you - a tee shirt or something soft in her crate with er with a peanut butter stuffed kong to keep her busy and your smell to keep her strong.
Make her enviornment calm and safe - don't push into doing things or being triggered. Do not set her up to fail set up all treat games, walks etc. to be at her pace, and be good times only. Try not to comfort her too much when she is scared - as it reinforces the fearfull behavior as a way to get attention.
Do you have a special walk place - a state park - a beach a dog run where she is especially happy - if not make one. When she gets there she gets yummy treats, when she is walking head up and happy yummy treats - on and on and on, until she has a happy special place to relax and feel safe. This saved one of our dogs. She went from so scared and withdrawn to racing aroud the car, doing her stampy giddy happy dance to get to "her place."
Be patient, take things are her pace, ignore bad or scared behavior and praise and treat good behavior. With time and trust she'll come around - a month is not a very long time. Even the worst bred dog can be trained and conditioned with patience and support - genes might be part of it - but any dog can become a better dog.
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Alicia,Owned by 2 Shibas, Niko and Avari, 3 cats, Miss Kitty, Mr. Grobbles and Al E. Cat and 2 beautiful daughters, Gwen and Penelope