Frankly, your dog was in a heightened mode, in a new home, free access to a dog she does not know. She works fine in your home with your Yorkie and your older lab.
The problem is that you brought it another female. That female is not reaching sexual maturity, and your GSD bitch is simply not ok with having another bitch there.
I think that you should rehome the Golden puppy, and be a three-dog home while you have a GSD.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC