Whatever you do, don’t stop treatment. Follow the doctor’s advice, but at the same time use critical thinking, and seek a second opinion (from a doctor, not alternative medicine) when in doubt.
As for coping from her side - be understanding, encouraging and accepting. If she loses hair, or gets bad skin - don’t make it a big deal.
Choosing treatment is a very personal thing. My father chose to stop his chemo treatments and it improved his standard of living dramatically. (he's still fighting cancer) A friend of mine (a nurse) said she'd never torture her self like she's seen so many people do with some treatments. (She died of cancer a few years ago)
Sometimes other's people's advice isn't based on what is best for you, but on an aggregate across many people, and you could be on the bad side of percentages.
As for coping from her side - be understanding, encouraging and accepting. If she loses hair, or gets bad skin - don’t make it a big deal.