That is a great question and the answer is possibly yes!
You see the herb that is in the coffee, the ganoderma, actually acts like a detox. The herb will cleanse the body rather quickly and diarrhea can be a side effect along with upset stomachs.
Bad toxins have to come out of the body somehow but it should settle down after a few days. I didnt get the diarrhea but I did feel like I had a bad head cold for days after drinking the coffee but it gradually went away and I have been feeling great since drinking it.
So unless it gets severe I would encourage your Mom to stick with it and she should start feeling better soon. Hope this has helped answer your question.