Bless you for taking her in. Let her eat as much as she wants, and then be sure to stimulate her pooping like that link describes. Love and care and food, and hopefully she will make it. A mother cat might abandon a kitten for any number of reasons, but the old myth that if a human touches one she will reject it is just that, a myth. Just as not every human is a naturally good mother, not every kitty is either!