I would like to add, take her out IN THE MIDDLE of play. When they are running around, full of puppy crazies, their systems get moving. They need to go and don't realize it till its too late.
As for the mouthing, welcome to GSD puppyhood!!! Pick a method and stick with it. Nothing works immediately. What worked for me was a high pitched squeak, followed by moving a toy around the floor and having him chase it. Over and over and over and over and over again, daily. For a few months. It does get better.
Also, remember that pups are a bit like kids, if they get over tired they get really really bratty. I used the crate during those tunes to force a time out and make him take a nap. It's not punishment. If he is being a demon, and you have fed, watered, exercised him, and he is still a demon. Pick him up, put him in his crate, with a chewey and let him nap. Don't make a big deal of it. No yelling. Just out him in it.
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