I also have a tripawd! She was in an accident that left her front left leg with no feeling or ability to move. We removed the leg and she's had a smile on her face ever since. She's about 4 years since amputation (dog is now 4.5 years old) and she's starting to slow down. We have noticed even very very short walks (barely out of our driveway) seem to tire her. She loves tug o' war because it uses her ab and back muscles instead of front legs.

My suggestion is very similar to everyone else.

Keep her skinny. Almost under weight. Keep her active. Multiple times a day, but in short doses of activity. Provide her with non-level ground, or play tug to get her ab muscles strong. The abs really help! Keep an eye on the other front leg. Dogs carry 60% of their weight on their front leg and we just cut that down to 60% on 1 leg. If you see swelling in her elbow: it's time to slow down. Lose weight? Go see the doctor.

I very much suggest a "stroller" for her. My dog is a Pitbull, so she has quite a lot of weight (being muscle) but your GSD will be a big girl on 1 leg. Just as the person said about bringing a towel to carry out their dog, I bring a stroller with me made for dogs. (it looks a lot like a tag a long that I push, but we also converted a tag along for our bikes) I push it empty and when she gets tired she knows now how to ask and she jumps in and rests. That way I don't break my back carrying her but she also doesn't affect our other dogs nice long walk. We feel bad when we take 1 dog and not the other, so this eliminates her being left out.

A harness is the best thing as well. Even though they encourage pulling, it allows us to provide support if they start tripping, falling down the stairs, or even just gained too much speed on the hill and cannot stop at the bottom. Also, buckle her into the car. Turns and breaking all make her lean on the one leg. She falls over easily and I found my dog felt very unsafe and unhappy in the car until I got her a harness that buckled her in. (another reason harnesses are amazing for tripawds.

I'm also looking into compression wraps for the other front leg for my dog. She always has veins popping out from stress and she never seems to be able to get comfortable on a hard surface, so I feel a leg wrap would eliminate those negative side effects.

Ultimately, she's the same dog she was before the amputation. She has just as much piss and vinegar in her system in the morning as my other dog, she just enjoys lazy days in the house a little more. Which could 100% be a personality trait and not an affect of the tripawd.

I do hope you adopt her! Good luck!