We got a black kitty from the pound she had been there almost 6 months after being taken by the human society from a crazy cat ladies home. She is affectionate when she is out. But on any strange street sound she hides and we can't find her. She had a brother and a sister there to. But we only adopted her should we have adopted the brother also to make her comfortable?
How long has it been since you adopted her? It can take some cats up to a year to adjust to a new home, new people, new sounds and smells. when I adopted my cat, she spent the entirety of the first month at home hiding under the dresser, leaving only to eat and use the litterbox and only when she thought no one was in the room. Now, she is very friendly almost never hides. So my recommendation is just to give it some time and see how she does