This really is just common puppy behaviour. Cant you leave her out in the yard permanently? You just have to be firm with her until she learns, german shepards are just really hypo in general and must be walked daily, she's probably just really bored. She'll be fine with the cat, she just wants to play, kitty will get away quickly anyway so dont be worried about that. Using a shock collar on a 14 week old puppy I wouldn't advise however..
We recently got adopted a 10 month old doberman, who really is still a pup, we have a yorkie that she things she can play with and play very rough, its been tough. We finally got her to stop biting by using a water spray bottle, dont know if its right or wrong but its harmless to her and it works. She sees the bottle coming and stops now. * * * Unauthorized advertising deleted by Moderator * * * Bill hope this helps.