My sister has the same problem as you. Took in a couple feral kitties from the same litter that found their way into her garage during the winter. The brother is tame as can be but the sister will not come near you. My mother after a couple of months has gotten her to enjoy being brushed but its hit and miss with her. Time is the only thing you've got going for you. In time she may feel comfortable enough to become one of the family.