The fact that you have been to the vets does not rule out a possible physical problem. Dogs don't have glass bodies and problems can be difficult to diagnose.
Don't placate her when she whines and try taking her for extra walks to occupy her mind. If she continues to whine, go back to the vet.
Is she eating and are her stools OK?
Has she had any shots/vaccination, worming tablets or flea treatments lately, perhaps she has been upset by this. In any event don't be tempted to give her any treatments until you have sorted the whining problem out. Just one last thought, could she have a digestive problem. If her food contains grain, this could be the problem. Dogs often have a problem digesting grain, if you change her food, do it slowly by adding a small % of the new in with the old. Increase the % every day over ten days until the change over is complete.