I am still very new to all of this having just got my GSD 7 months ago, but...
I went through something similar with my pup - except her jealousy was focused on my cats. She would whine and bark a high pitched bark whenever my cat would come get affection from me or try to butt them out of the way. To let her know that behavior was not wanted and would not get attention from me by behaving that way - I would pick the cat up and walk out of the room, ignoring her when she acted that way. At first she just whined more, but then she caught on that if she sits calmly too I can pet them both at the same time or she gets extra loving when she has been patient and calm when I am showing affection to one of the others. She learned that she cannot get my attention by being a brat to the other animals in the house or bullying/demanding my attention whenever she wants it. She has to earn it by having manners.
It sounds like your puppy is still young, so I wouldn't really correct her behavior, but you also don't want to reenforce that if she acts that way, she can demand the attention. Somehow figure out a way to teach her that she needs to remain calm when you pet your other dog and that she can earn your affection that way.
Hope that helps and good luck!