28 lbs is still huge. A 28 lb puppy, if growing at a steady rate, would likely mature at 100 lbs. My nieghbor owns GSD's, and his largest girl is a little under 70 lbs, which is the limit for females. I truly hope the female has had her hips & elbows, atleast, certified. Her being very large doesn't help the odds that there are joint issues.
I really hope you consider training both of your girls!
It's very fun, and it proves more than the "bloodlines" of your dogs. There are loads of "pet quality" dogs with amazing pedigrees... lineage does not fully determine the breeding worth of any dog, IMO. Any GSD needs to be SCHI titled to be proven as worthy of reproducing, the likelihood of a dog being injured in Schutzhund is just as great as a dog being injured while playing frizbee in the backyard
. That is a minimum to me, preferably seperate Tracking & Obedience titles should also be attained.