German Shepherd advice

Hi. I have a pup about a year old, and she clearly has some German shepherd dog in her. She seems to have the temperament -- shy but aggressive when she's scared, and she's scared of everything. I'm not sure how best to handle this. I am very adept at dog training, but have never had a fearful dog before. I carefully introduce her to many, many, MANY new situations, people and animals routinely, and she likes everyone after that initial growling tail-tucked incident. She loves the dog park, loves kids, accepts guests in our home, but with every new moment she seems nervous and anxious, does a lot of stress-yawning and stretching in the best of circumstances, and in the worst (July 4 neighborhood fireworks) comes completely unglued and tears around in blind terror.

Does anyone have advice on how to make her more confident from the get-go? She's a good pal.