Irritable Bowel Syndrome Treatment

The symptoms are so similar , how does one diagnose one over the other.
The significance of the two diseases is so different.

She has diarrhea, and has had it for a long time. she doesn’t have worms or enzyme insuffiecy. And how can I help her? I’ve already tried rice, chicken, keopectate, different kinds of dog food, and yogurt.
I’ve taken her to the vet alot! and have spent alot in tests and medication. the vet says its probably irritable bowel syndrome and that we should be careful about stressing her out, like don’t get her to excited.

I have a condition in my rectum called acute colitis with cryptitis or inflammatory bowel disease. Will prebiotics and probiotics be helpful for this condition? Also, will aloe vera juice help? What alternative treatments are there for inflammatory bowel disease instead of taking prescription drugs?