New Amy Woes

Now we have a new problem with the pup. Digging. The people behind us have several dogs, and Amy wants to meet them. I mean she really, really wants to meet them. She's always enjoyed digging along the fence line, but nothing like this. I'm at the end of my rope with it. She can get her head under the fence, and I'm scared she'll hurt herself. Or get the rest of her through and take off and get hit by a car. Filling the hole again does no good. She merrily digs it again. We may have to put rocks all around the fence line. Say goodbye to a couple thousand dollars we don't have. Any ideas? Shock collar? Electric fence? I'd hate both, but I'd hate seeing her hurt more.