Thanks for rescuing her! My advice would be take things real slow, let her adjust in her own time. It's impossible to judge whether her timidity stems from her surroundings or her heritage, but either way you cannot "force" socialization. I took in a 1.5 yr old female GSD that seemed not very sociable and a little timid. It took her a full 3 months to begin to be comfortable enough with her new surroundings to start to come out of her shell. And it was a couple years before she was completely over whatever it was that caused her to act that way. So again, just show this puppy that she's safe and that she can trust you always, then in time you'll see her true nature. Congratulations on the new puppy, and welcome!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain