Did you say you have a fence? If you're in a safe area and have a secure fence, you could probably leave her outside when you're gone if that's where she feels most secure. When I was growing up, our family dogs always had a dog door that led into the fenced yard, and they came and went as they pleased. These days, I don't leave my dogs outside when I'm not home because I worry that if they did somehow escape the fence, our neighbors might shoot them--we live in a rural area, there are chickens, cows, horses, ect, and I worry that a GSD might be seen as a threat to the livestock. For a little more security, you might consider building an outdoor kennel and a run. If I wanted to leave my dogs alone when I was gone, that's probably what I would do. Good luck. I hope you find a solution that works for you.
If you think she'll dig under the fence, here are some things you could try:
Bury chicken wire at the base of the fence. Be sure to roll the sharp edges away from your yard.
Place large rocks, partially buried, along the bottom of the fence line.
Bury the bottom of the fence 1 to 2 feet below the surface.
Place chain-link fencing on the ground (anchored to the bottom of the fence) to make it uncomfortable for your dog to walk near the fence.
For more detailed advice, read our instructions for keeping out burrowing wildlife.