You didn't say where the cancer is exactly so I can only guess at where the doctors are wanting to do the radiation. My sister in law had radiation last fall from mid-September to right before Thanksgiving on the cancer in her lymph nodes in her neck, in her brain and in her chest every day except Saturday and Sunday. By the time she completed the required number of sessions she was so burned that her skin was black and falling off as if she'd been in a fire. She tried every cream and ointment that they recommended but in the end nothing stopped the pain. She has permanent scarring.
The radiation did temperarily shrink the cancer in her neck and in her brain, however, it came back.
I'm really sorry for what you are going through. Believe me when I say I know it's not easy watching someone you love suffer.
I wish that I could give you something positive and tell you that there are no side effects and that the radiation is pain free but that's just not the case. Whatever she decides to do, just support her the best you can.
God Bless you both, Theresa