Sharing is an important concept in our family, but I can't seem to communicate it to my child. How can I teach this to her?
I believe that sharing is a natural impulse. Most kids will automatically share their food, toys and money. If they don't, it's frequently because they're afraid that there won't be enough left for them or that they'll have to give everything away.
You might try explaining to your child that she doesn't have to give away everything she has, that it's OK to have a special place and special things that are hers and hers alone. This teaches its own lessons about respect for oneself and for others, and it will help her realize that other people are allowed to have special places, too. If you help her establish a special place and talk about how, from now on, this will be just for her, you're showing her that you respect her and that you'll honor her privacy. At the same time, you can continue to stress that privacy and sharing can coexist.
And don't insist a young child like yours share all the time. It's not realistic. You have to decide what rules you will absolutely never bend on, and which ones you're going to ease up on from time to time—even though the rule is valid. Sharing is important, but there are some ages where territory is incredibly important to children, and you just have to roll with the punches and keep making your points as best you can.