Did she ever have kittens herself? I keep telling the guys at work, "Once a Mom, always a Mom"... I just adore it when one cat will adopt a kitten... I had a male cat years ago that I kept having to get kittens for. He LOVED playing "Daddy Cat" to kittens and would even let them "nurse(?)". Oddest thing I ever saw but he was one of those once in a lifetime kitties.