Off topic - Anyone ever had radiation?

I’m hoping someone on this site can give me a bit of an education. My sister is currently going through radiation treatments for breast cancer. They had to stop the treatments because she is very burned. She has 8 left. I can’t seem to find out much information on what happens to the skin around the treatment area, how it heals or what happens. Every site I go to say mild skin irritation. My sister has more than mild! So can anyone let me know know what she can expect. How does it heal? How long does it usually take to heal? Will she peel? IS it like a sunburn? will she scar? My sister has enough on her plate and I just don’t want to bug her with trying to figure out what she has left to go through. But I want to know so I can at least empathize with her.

Thanks for any information…