Your mother is most likely having a late complication of diabetes called as autonomic neuropathy. Other possibility is recurrent infection. Please get her checked for other complications like kidney and eye involvement. For the diarrhoea, presently give her a course of Tablet On twice a day for five days. If there is no response, then give her Lomotil twice a day during attacks of diarrhoea. If diarrhoea, still persists then contact us again. We have few more modalities available to treat her.