I'd love to hear what people have to say as well. Brooke has developed this fear as well. We have to go to her pillow and pull it out from her to make her stand up. then she shakes but will eventually let us put her collar on. Once she's out and sees that everything is fine, she stops shaking and enjoys her walk. I suspect it is because thunder and fireworks occur at night. She's food motivated, but nothing is good enough when she's stressed. Now that it's getting darker earlier and earlier, doesn't help either.
Brooke will walk though, albeit still a bit nervous but eventually she's ok and will enjoy her walk once she gets out the door. The only issue I see with your situation is allowing her to determine when to go back in. Maybe you need to take her for a short walk, just long enough to be the one who decides when it's time to turn around and go back in...sort of desensitize her slowly.