Outside of the fact that she is probably bored and lonely, and you probably need to give her optional recreational activities, you could try placing a few pieces of her feces in each hole she makes. That would at least prevent the re-excavation of previously refilled holes.
She's bored..... Exercise her more and give her something else to play with. My Pitt was a horrible digger and he ran 3-5 miles a day. I finally got him a large plastic ball. It's actually a horse toy but he chases it all over the yard and plays with it like crazy. He hasn't dug since he got it. He's inside most of the time and only out when were all gone so that helps too.