I guess there is no way of knowing if her fear is due to lack of socialization or to a genetic glitch, but you can probably make it manageable with a lot of work.
You must make sure you never put her in a position that causes her to feel fear. For now, I would suggest to put her in her crate, or gated in another room when people come over. After they are seated, you could give them some treats, then let her out. These treats should be something FABULOUS, that she gets ONLY when people are in the house.
Let her come to them in her own time. Ask your guests to completely ignore her - to not even look at her. When she does come close, have them toss the treats to her, still without looking at her. Never lead her up to anyone, or have them offer her anything from their hands. She MUST feel that YOU will keep her safe, and that she does not have to defend herself.
On the street, when she starts to show signs of fear, do some obedience drills with her, and give her really great treats if she stops acting fearful and obeys you. These treats should be the same as above. Teach her the "Look at me" command and use it when you see people approaching. Have her heel or sit. As she succeeds from a distance, you can start getting a little closer.
Is she a food hog? If you get too close to people and she shows fear, toss treats into the air and let them fall around her. The aim is to make her think - "When I see people, hot dogs rain out of the sky".
The most important thing of all is that you must IGNORE her fear - never ever soothe or comfort her, as she will take that as praise for showing fear.
I had foster dog who was hysterically terrified of everything - parked cars, shadows, garbage bags and people. This method did work for her!