Hmmm no medications and none of those foods? Was this a loose stool? If food passes through the GI tract too fast it can cause that. Has she had any symptoms of gall bladder issues? (pain/pressure upper right quadrant under the ribs) Mine was pressure not real pain. Since the gall bladder stores the bile I'd imagine if it's blocked ducts she'd be having other symptoms to some degree. Of course she might be, but dismissing it as gas or something else. I ignored mine for weeks before it became so irritating I finally went to the doctor.
I experienced it a few weeks ago.........I'm guessing it was medication related and also due to having to drink so much V8 juice to make sure I was getting enough vitamins because I can't eat like normal people right now. I backed off on the V8 and it stopped.
It doesn't sound serious which is a good thing. And no Jo, you can't gross me out, I do this for a living. lol 
