Hi & Welcome.
I can understand your concerns for your beloved mother.
The most common side effects of
Buspirone (an anti-anxiety medicine) may include: headache,
dizziness, sleep problems (insomnia), nausea, or
feeling nervous or excited.
However, it is unlikely to cause diarrhea.
Whereas the oral antidiabetes medicine is known to cause
heartburn, abdominal cramps, bloating or
flatulence and diarrhea as its common side effects.
She may need dose adjustment of Metoformin or an alternate effective but a safer medicine to control her blood sugar after consulting her physician.
Hope this will be helpful.
Best regards.