She isn't spayed, so that could potentially be it?
The only ever interacts with my parents neutered old dog (lives with) who has nooo interested, my BO's neutered poodle and my neighbour's intact female boston. Because she's really hit and miss about other dogs she doesn't go to dog parks or any setting that would put her near other dogs.
What would set off that behaviour?

She was at the barn with me again today and didn't once dig, but she was also occupied with the farrier tossing hoof clippings at her. I did catch her sprawled out napping on some hay bales, but oddly enough it didn't look like she was digging before lying down. Bales were intact.

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