Just give it time. Mrs. Maya (we call her MRS. because when we got her from the Humane Society, she had been knocked up and they didn't know it and she gave birth to one ONLY ONE kitten in our home, which we kept, of course) was absoluted terrified of everything for the first two years that she was here. It was to the point that after she popped out her kitten, she immediately fled and hid under the couch that was in her birthing room. I was worried that she would reject her kitten, but as she was in a safe, closed room by herself, things turned out just fine. It literally took her two years to be able to sit half on my lap to get petted -before, she would jump up, roll around, panic, and run away. Today, three years later, she is ALL OVER ME, and just started feeling comfy enough to knead away. Thanks for adopting a feral cat! I am currently in the process of trying to sort one out in our neighborhood (first the food, then the trust, then the humane trap, then the NEUTERING, then the taming into our home...), and hope that he fits into our family of four kitties one day.
