I’ve worked with individuals with a colostomy bag. However, they were wheelchair bound.
Personally, I would be more concerned about what other health conditions your client has been diagnosed with and design the program around her clinical conditions.
The American College of Sports Medicine is a good resource, however, I have not found anything regarding training an individual with a colostomy bag.
A good way of thinking about the colostomy bag is refreshing your understanding of the digestive system. The colostomy bag is essentially the finish line of her gastrointestinal tract. Don’t let it frighten you. She simply evacuates differently than you and I. However, it is still evacuation.
Since she clearly is accustomed to living with a colostomy bag, she recognizes the precautions she has take as far as bodily fluids and odor are concerned.
I, however, have never had an uncomfortable experience with my clients.
If you feel unsure, you can always speak with her doctor or speak directly to your client. She will likely be your best resource.