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She needs to see the vet. Yellow stool indicates one of two things in most cases - either a bacterial imbalance in the gut which almost always requires antibiotics. Stool that is light like this can also be from an over production of bilirubin which can indicat liver problems. With her belly being distended like this, I'm concerned about the possibiity of something going on in her liver that could be serious - possibly a malignancy. Please have her seen in the next day or so.
Let me know if I can help you further.