Aggressive Behavior of New Puppy

Question
On Friday I received an 18-week-old german shepherd from the midwest as a
gift. I was told the dog was socialized, especially with cats as we have an 8-
year-old cat. Upon her arrival, she was quite aggressive in growling and
barking at myself and my husband. She would not let us approach her. Only
today was I actually able to pet her and put her leash on her. She continues to
bark and growl at my husband on occasion. We took her to the vet today and
the vet was concerned with this behavior (as the dog lunged at the vet and
was very aggressive). At one point the dog allowed the vet to touch her, but
then later on went back to her aggressive behavior. The vet indicated that this
dog was not properly socialized and that this behavior may not go away. We
have left a message with an animal behaviorist to get an assessment. My
question is, can this type of behavior be resolved or is it too late to socialize
her properly? The vet kind of alarmed me when she asked me how attached I
was to this dog and that her behavior is a concern.  

Answer
This is a difficult question to answer.  Since the vet has seen her, I tend to accept her judgment.  Early socialization is important and some dogs never fully recover from a lack of it.  Some dogs do fine no matter how bad of a start.  Had you bought the dog, I would say the sooner your return it the better.  

Shepherds are slow to form new bonds.  The progress she has made is encouraging.  In some cases, vets are skilled in the physical side of dogs.  Unless the behaviorist is optimistic, you might best return her before your heart is broken.