How much time out is she getting? how much daily mental stimulation?
We have a big yard, the dogs are allowed to dig anywhere down the bottom end of it. Funniest thing I ever saw was Mac in terrier mode searching something out, then she decided Harry would probably be able to move more dirt faster, she got out of the hole, told him to get in then proceeded to put her paw on his head and push him down into the hole. "Faster Harry. EFFICIENCY! GO!"