Ginger has good suggestions.
Also, you can try a squirt bottle. When you see her doing that, squirt the water at her and give her a firm No!!!
Yes, she needs more structured accompanied exercise to use some of that boundless energy she will have at her age. And some breeds have greater need for exercise than others. But all dogs -especially youngsters -need some work to do, something to burn that energy.
What's happening is she is finding ways to do some work. She is trying to invent a way to use energy. But she will get obsessed, the more she does this, the more ingrained it will get, until that will be all she will want to do!
Distract her with good long walks if at all possible, plenty of running, and 'fetch' games...frisbee...etc Get her away from the garden and spend time walking her. When she comes home, all tired out and panting, she will probably be able to flop down on her bed and rest.
You can expect she will go back to the grass-pulling now and again. She is having fun doing it! A firm "Hey! No!" as SOON as you see her begin to dig should work to make her back off, and each time she stops make sure she is well rewarded.