Hi Kim,
Tl/dr: yes to what Dr. Thomas wrote.
I have been participating in various forms of treatment and recovery for 3 decades while running around the mountains. Radiation, experimental chemo and 4 surgeries. In my opinion all of the studies and resources may be useful, but the patient will have her own experience. I would have her listen to her body. Following the warm-up method of “I’ll just run slowly for ten minutes and see how I feel before deciding to continue with workouts” may suffice to avoid over-training / exertion. Steve and Scott have here, and in other writings, recommended listening to the body with more eloquence than I state here. Just remember her experience is unlikely to be linear. There will be set-backs. There may be days when she unexpectedly feels fine. Outside of protocols which hammer her immune system, the doctors may let her exercise according to her own wishes. My 2 cents.