New addition needs lots of help! Anxious and Afraid of everything!

Our family adopted an 8 month old king cockapoo about a week ago. She was kept outside with other dogs by her breeder. First day we brought her she was very playful and happy. Slowly she became very shy and anxious. She is terrified of everything. Noise, people, movement. She is so afraid that I have to sit with her and try to get her to eat. She won't eat dog food. Today I made her white rice and chicken since she hasn't been eating, and she finally ate. I really need help and advise on how to get her to stop being so afraid. When shes outside she's a completely different dog. Walks on the leash, tail up, barks sometimes, very happy. I know she needs time to adjusts to being inside but I need advise on how to help her. I don't want to encourage this behavior and if I ignore her she just tries to hide in the bathroom. Please help!