Puppy shy and occasional growler at strangers

We have a five month old German Shepherd puppy (mix) that we picked up
from a shelter on January 1st. When we first got her she was very shy.
The first two days she would barely leave her dog bed. Over the first
few days she warmed up to me and my girlfriend and she loves our 5 year
old shepherd mix. She is still shy with strangers and we noticed that
she will growl. She has no problems with other dogs. We take her to the
dog park and she will play, but a little wary of going to other owners.
However we have yet to notice her growl at the dog park.

My girlfriends 2 year old niece, especially from the high level of
energy, is a prime candidate for growling. However yesterday, despite
growling at the start, she started to sniff the child as well as let
her come up slowly and touch her.

Then last night we were at my brother's house and another friend was
there. Our puppy was growling quite a lot and barking from time to time
if there was too much sudden movement by the strangers. She started to
warm up by the end of the night and was much different when my brother
had removed his hat. Earlier in the day we introduced her to my cat at
my house and the dog was open, interested in the car but not chasing.
It really seems to be limited to strange human beings.

The question is what can we do to help open her up? No one has any idea
what her formative socializaion period (2-4 months) was like, so we are
assuming she had little socialization. We have been starting to...

a) Take her to the dog park to get out.
b) We are going to have our niece over and visit her house once or
twice a week.
c) We are going to enroll in a puppy socialization class.
d) We are going to expose her to new people and environments, such as
my brother's house, as much as possible.
e) When out we are not just staying in one place. For example, last
nice we made sure to hang out in the kitchen and she would come in at
her leisure and hang around and walk back and forth. Just trying to get
her ok with the idea of other people.

What other things can we do? We don't want to have a full grown German

Handsome Jack Morrison...

1. Have your dog assessed by a competent trainer/behaviorist,
preferably one who's experienced with German Shepherds.

2. *If* your dog passes muster, immediately find a good OBEDIENCE
TRAINING class or instructor and start OBEDIENCE TRAINING your dog.

And you need to do this ASAP, because you might have a very serious,
even dangerous, situation brewing.

Your dog almost certainly had very little socialization to human
beings early on, so couple that with a GSD's natural wariness of
strangers, and you're not likely to end up with Rin Tin Tin here, no
matter what you do from here on out.

IMO, until you can find this person, and have him/her look at your dog
in person, you should not allow her to be around small children.

The growling is a *bad* sign.

IMO, you need some help, and ASAP.

Shepherd that is wary of strangers. The only blessing so far is she has

Handsome Jack Morrison...

Then why did you get a GSD?

not shown any signs of attack and she seems to warm up to the person as
the visit continues.