Besides walking and playing fetch, what fun do you have with your dog?
It may almost seem like an aside, but an older gentleman recently asked me, "what is the most important aspect of dog training"? My response was the bond you cultivate with your dog! EVERYTHING else you do stems from, and is either facilitated by, or frustrated by a lack of, your bond with your dog! That means spending time, not just active time, but idle time as well. Being silly, playing, AND letting your dog just be a dog with you present (because you being there is VERY important for them, regardless of the breed, but for GSDs even more so!). I think people underestimate the POWER of this, because it's not such an active and for some folks not so intuitive a thing, but IMHO it's much more important than any other training you'll ever do.
And if you truly establish a strong bond, with any dog, all training for any purpose will go much more smoothly. It's worth the effort, it has HUGE benefits for both of you, and best of all it's easy and fun!
OP, another thing to consider is that since your dog is still young, you take her out to play and walk just before putting her in the kennel. Try building in a little relaxation time after the walk and the play to let her calm down before kenneling her. Just sit with her in the yard for a few minutes, calmly, giving her a better chance to switch gears. You can't train a dog not to be a dog, but if you can imagine the world from their perspective, sometimes it can be easier to alleviate the tension between your, and her, reality!
And from your other thread, PLEASE PLEASE PLEASE don't treat her behavior as an issue you can train her out if using an e-collar! E-collars are great training tools, but here I think a little perspective and some subtle changes in your current routine will benefit you both.
In general think of training as eliciting and rewarding desired behavior, not as a means of "stopping an undesired behavior". There are exceptions of course, but the perspective above will get you further faster...again, in my opinion! Good luck, and enjoy your your dog, first and foremost!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain