Friend, it is not normal for her to go to the litter box in the middle of eating. The fact that she has diarrhea it is likely a response to the inflammation in the colon (large intestines). The big question is: Why does she have diarrhea? Diarrhea can be caused by many different medical conditions. It will be difficult for me to determine the exact underlying cause without a hands on examination and some testing. But, common causes are: Diet, autoimmune (IBS), infections, or even part of a systemic disease to name a few causes.
In this case, I would recommend a hands on examination by family veterinarian given that this has been ongoing for 1.5 months. In the meantime this is what you can do:
1- Do not give things like Pepto Bismol or imodium.
2- No food or water for 8-12 hours, need to give her gastrointestinal tract time to rest. Then, offer small amount of water followed by a diet of rice (50%) and boiled boneless chicken or ground beef (50%) until the stool is back to normal then wean her back into her regular diet.
3- Supplement with a probiotic (fortiflora), these are friendly bacteria that help with regularity. You can buy this over the counter in any pet store.
4- Follow up with your family veterinarian for a hands on examination. If cost is a concern look into your local ASPCA or Shelter where they often offer veterinary services at a lower cost.
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