the vet was very concerned about it because the pup growled several times during her check up.
I can't comment on whether the puppy actually is aggressive or not, although I would lean towards saying its just a normal ill-mannered puppy just because the odds are in favor of that.I know vets aren't the best source for behavior advice but I was still surprised that the vet voiced her opinion so vocally about something being "off" with the puppy.
But I just wanted to share about a vet experience that showed me how much some vets know (or don't know) about behavior.
When I got Chester (1.5/2 yrs old from local Humane Society) I of course made a vet appointment for a couple days later. I hadn't had any pets here before, so I just found a close by vet and went in. The vet has horrible "bedside manners"- he seemed competent enough medically but just couldn't relate to the dog at all. I'd told them he was new to me and I didn't know if he'd ever had traumatic times at a vet before. So during the exam, Chester was panicking, trying to mouth (like, touch teeth to hand and shove hand away), and get away.
The vet told me that Chester was a danger to society, that he would chew and destroy everything in my house, that I would need to muzzle him in the park because he might bite children or people, and he would need to be crated securely when I was gone. Instinct told me the vet was a completely dummy in this regard and I ignored him.
Of course, Chester is perfectly behaved inside, he has never been crated with me at all, he LOVES people, he has had small children stick entire hands inside his mouth, their faces in his face, grab him in bear hugs etc and all he does is happily lick tiny faces and hands
what I'm trying to say is, it is worth finding a good trainer and/or asking around to find a vet that has good behavioral knowledge not just medical knowledge. I found a great vet's office (team of 3) who deals well with everything from the overenthusiastic Chester (he loves them so much he tries to tackle and lick to death everyone there) to fearful dogs who are trying to bite them.