It's great of you to advocate for your sister and glad to hear she is doing well!
The one similarity we can all agree to regarding breast cancer treatment is that no 2 of us have the same side effects. Fatigue is a very common side effect of radiation treatment. Some people I recall needing to nap during the day it was so severe. I felt pretty good throughout mine, even though it was after chemo. I did find myself going to bed a little earlier, but I kept up with work and house and yard chores...no kids though to take care of, that would certainly add a lot to one's plate.
Yes, here many cancer centers offer the "body-mind-spirit" type complementary services, including massage and reiki, as well as art therapy, journaling classes, etc. It is a great way to get people together and certainly to offer some relaxation and tension relief!
Keep us posted and wish your sister well from across the pond!