Brief Answer:
She needs further investigation to find out underlying cause

Detailed Answer:
Hello XXXXX
welcome to Health Care Magic

I really appreciate your concern and I can understand your mother's problem that how troublesome is the issue.

Since it's been 2 months and colonoscopy report is normal, So in my opinion there might be any underlying cause for this long standing diarrhea either infection owing to poor hygiene or food allergy or any other metabolic disorders like thyroid disease or in very rare condition, certain cancer may cause long standing diarrhea.

So I would advise you for a battery of tests like stool test for ova, cyst and Protozoa as well as for occult blood, Blood for Hemoglobin, CBC, liver function test, blood sugar, thyroid test, HIV test, an X Ray chest and an ultrasound abdomen.

if she has already undergone any of these tests(since you've mentioned that the blood tests were already done), please upload me the reports and write back to me with these details-

Her weight and BMI
Has she lost some weight during this period?
How's her appetite?

Meanwhile continue with all the medicines as her doctor advised ,

Ask her to have plenty of fluids including ORS to maintain good hydration and to counter electrolyte imbalances.

Ask her to wash hands with disinfectant hand-wash every time she uses wash room and before eating.

Hope I could answer your question, Please feel free to ask for follow up question with all the details I have asked so that I will be able to tell you more accurately.

Waiting for your reply.

Best wishes

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