Could also be that maybe at one point something with a thorn scratched or poked the dog. She could have also seen a small animal or insect that spooked her. Panting is a common sign in dogs who are having issues with anxiety, my friend had a dog who would pant and hide during thunder storms. Hope this helps!
Tony's idea sounds probable. Something out there bit her or spooked her in some way ( an ant? a bee? My dog wouldn't go NEAR any place where there were ants!)
It could be something else, something you wouldn't know about -for example if she suddenly got a twinge in her belly or her leg and it happened at a certain spot, she might associate that place with the sensation...just a thought.
Oddly, I am dealing with a cat who is suddenly 'spooked' about the room where her bed and her food is. (The cat isn't mine but belongs to a neighbour, and I am going in twice a day to feed her & socialise with her.)
Anyway, she was refusing to go anywhere near that room. Weeks ago a dog poked its face through her cat door, and she will not let go of that. She hates dogs!
I am working with her but it is a much slower process than it would be with a dog!
So what I do to ry to relax her in that space is I get her cat biscuit box and rattle it, then put one bit of food down just outside. When she looks at me for more, I put another bit down a bit closer to the room....and so on. I have managed to get her to enter her room, and stay for a few minutes using food treats as distractions and enticement to go into her room.
I wonder if you could try to entice your dog outside by using treats?
Or by sitting in that place calmly (maybe take a newspaper or book to read), and rattling a box of biscuits or something so that your dog might venture out there, and start to associate that spot with something positive instead?
Hi. This sounds like a reaction to something like maybe an insect that bit her - or maybe one that just surprised her - and now she's nervous of going on it. Try not to make a big fuss about it, as she will feed off your own anxiety and concern. I'm sure she'll be back to normal in a few days.
Tony