DH had a tumor in his frontal lobe in his 20s. He refused western medical care (and had to hire an attorney to keep the diagnosing doctors off his case when they were threatening him with being committed and having care despite his wishes). This tumor was not malignant, but it was growing so fast "they" gave him 6 months to live without their treatment. He refused b/c they said surgery wasn't possible, and it was only radiation being shot at the frontal lobe...the side effects that were possible, he felt, were worse than death.
He went on a beyond-macrobiotic diet, where he coudln't even have fish (usually a part of macro) b/c the fish readily available in the States are so toxin-filled, he juiced, he did supplements, he did hyperbaric chamber treatments. He paid out of pocket for it all b/c they aren't covered by insurance even now, and it was crazy-hard (he had to move back in with his mom) b/c he was making under 30K at the time while in the Seattle area.
He also paid for MRIs throughout, also paid for OOP, and within 6 months it was responding. Within a year, I believe, it was gone.
Diet CAN have affects even on scary "cells growing and not stopping and creating tumors" problems.
I remember reading
this article when it came out. 1/3! From the article, "The genes have been there for thousands of years, but if cancer rates are changing in a lifetime, that doesn't have much to do with genes," said a Harvard researcher. As stated in the article, the problem is EXACTLY what happened here. People hear this, and feel BLAMED. Instead of feeling EMPOWERED. That they can affect change in their internal environments. Make a chance. Do something.
I believe that someone with a scary diagnosis should definitely do everything to make their bodies not have to fight the tumors AND have to deal with junk being put into them. So yes, I think your sister should be helping her body...not hindering it. She could feel empowered by such a thing...no need to feel guilty.
By the way, if she has her thyroid out, tell her to get a careful surgeon. Friend of mine had that surgery, the guy nicked her parathyroid and had to take THAT out, too. It's VERY VERY VERY difficult for her to manage her weight now, and she has to take something like 30 calcium pills a day, last she told me, because of not having either one of them....