How can I make my cat comfortable in its new surroundings?

My six year old cat is adjusting to the new house and backyard wonderfully, but my two year old, Ginger, just doesn't seem to be happy here. Ginger is a Manx and this is her first move. She is an indoor/ outdoor cat. She meows incessantly if she's kept inside and then disappears for hours if I let her outside. At our old house, she had a hiding place under the house and was always nearby. When I came home from work she was usually waiting for me at the backdoor or would immediately come to me if I called her. Do you have any suggestions for maybe building an outside "safe haven" for her so she's comfortable and doesn't feel the need to hang out in the neighbors yard. I fear she'll decide to live with someone else!!!