Diabetes is sometimes difficult to manage, so I am glad to hear that your mother is going to a clinic that is monitoring her so closely. Regarding her abnormal bloodwork
results, potassium levels can definitely go low when someone has bad diarrhea. Other causes of low potassium include too much insulin (her blood sugars would be really low too), medications (like water pills), and vomiting. Now that her diarrhea is better, this potassium problem should resolve.
As for her white cells being low, that can sometimes occur with bad infections. The usual causes of low white counts include cancers, immune disorders, and severe infections. Perhaps her diarrhea was from a gastrointestinal virus, and that caused her white count to drop. I would let the clinic monitor it, and see what happens. If her white count stays low for another month or so, it could be a symptom of another problem. Good luck!