Sometimes individual birds, just like people are less social. If you can figure out a favorite treat, thats a good way to help socialize her more. If she is the youngest, it may also be the pecking order of the flock. I can usually make friends out of just about any bird with a fresh handful of bread, and a lot of coaxing. Just take it slow and she should eventually bond more.
Thanks for the info. I have been working with her and so has my son. She is starting to get less fearful of us and today I saw her out in the pasture with her friend. She even came up on the back porch steps today. I'm encouraged that she is making progress. Yes, she is the youngest by a day and definitely the lowest in the pecking order. She is beginning to peck at the white millet I throw out in the evenings for the guineas so hopefully that will become a treat I can use!!