help very nervous 3 yr old

[marigeo90]

Hello everyone,
I have a 3 yr old female Shepherd. She is so sweet, but only likes her family! When new people come to the house she will bark and run away...if any of them approach her she will squat and pee while growling) and have her tail between her legs, and ears back! Any help or advice would be so appriciated! She loves attention, and i can tell she wants to love everyone, she is just very unsure of herself. How can i fix this?
Thank you
Marianne!