The average adult weight of a GSD bitch is 32kg, but obviously that is average there will be deviations either side. GSDs are not notoriously fat dogs and they shouldn't be because of their hips. Remember she will keep growing until she is 2 years old, so as long as she is in proportion she will be fine.
If you ever get to the big champ dogs shows, Royal Canin do an excellent book called the German shepherd Encyclopeadia, I got it free when I bought a bag of food but they might sell you one.