My personal opinion, after loads of research, is that chemo can damage one's heart as much or more than radiation. Radiation is very specifically targeted at angles predetermined extremely carefully before they even begin the real treatment. No beam of radiation should ever go through ones' heart.
I hope you and your wife have a good visit with the Radiation Onc (get one if you don't have one already). You will feel much better after the meeting. My first 'treatment' lasted a little over an hour so that they could map out the exact areas and mold a cast that exactly fit my body. I lay in the cast for each treatment. That was the hardest day. Be aware that she will be marked with paint markers that will be there for a month. A little hard to see at first, but after a few days, it's OK. Just another part of the journey to KILL THE CANCER!!!!!!! After that, it took longer for me to check in and change than it did for the radiation. I made some wonderful friends there. I never needed to take anyone with me. It was so quick and completely and totally painless.
I hope your wife has been taking CoQ10 during her chemo treatment. If not, please ask if it's OK. My cardiologist recommended it, so my Onc had no problems whatsoever. I take several supplements and came through with flying colors no idea if it was because of the supplements or not, but strongly believe in them.
My Rad Onc wanted me to wait a full 30 days after chemo before radiation began. Some gals say they were fatigued during rads, but I didn't notice it. I was tired, but I truly believe it was chemo and the realization that I could finally breathe than it was radiation. I started walking during my last four chemo (taxol) treatments and by radiation, I could walk over a mile a day. By the end of rads, I was up to almost 3! I think exercise (no matter how little) is the key to a good attitude and healing.
She may get a little sunburn toward the end of treatment. It can be quite painful, but it heals quickly. Again, hydration is the best thing!