Okay, here is an update.
I agree with Ruby and Labman that we need to be the pack leaders and we have signed up for an obedience class and have been reading books since the day we got her. We use calm assurance, walk through the door first, etc. Etc. She has progressively improved in her behavior since we got her, and we are taking a baby steps approach. This is just a disheartening setback because she loved to go for walks until Thursday of this week.
We took her to the vet for her thunderstorm anxiety, she does experience extreme panic, and we have put her on some natural remedies and installed a DAP diffuser in the house and she is wearing a DAP collar. The vet suggested valium if she gets extremely panicked, hurting herself.
I agree that two weeks isn't long enough, I'm aware of that. However, as stated in my post, she is not a puppy, so respectfully, much of that particular advice is not going to work for me as she weighs 50+ pounds. Also, she does *not* like to be crated whatsoever - she ate her way out of a metal crate with her previous owner and has a broken canine to show for it. She is much calmer when she has a place to call her own, but can enter and exit it freely - we have a few empty closets and a shower stall in our house that she goes to periodically to calm herself down or to chew a greenie.
Today we got her to at least hang out in the yard outside for a while, luring her out the door with her most favorite treats (pieces of hot dog) and sitting with her on the porch, scratching her ears, etc. As you suggested. We tried the starting behind her and saying "Go, go, go" which worked for a while, then she turned and ran back to house.
She loves to ride in the car so tomorrow we're going to try and get her in the car and take her to the park. Hopefully her confidence in us will grow with each passing day.
I appreciate your responses and all the suggestions here, they have been extremely helpful. Thank you.