Stop being so bloody obtuse.
That article is trying (and failing in my opinion) to gloss over things. But it seems that you prefer others to take it at face value.
Read between the lines of that article and take heed, for once and for all - chemo isn't given to those who don't need it. In truth, there is no such thing as preventative chemo. Chemo is chemo is chemo.
Oh, and in response to your earlier statement:
But a healthy young woman having preventative chemo should recover.
I do not understand why so many of you are talking as if she is going to die?
I am a healthy young woman (under 50) with a cancer. I was given chemotherapy because there's a very real chance it will return either the form of a new primary, or secondary. It might not be today, tomorrow or a few years time, but there's every chance it could, or it might not. No-one can predict, this is the issue with cancer and what they're trying to say. It's not about dying, plenty of people live for years with cancer, even terminal ones. This is something anyone who has been treated for cancer will fear, its possible and in many cases, inevitable return.
Unfortunately, this could be a very real thing for PoW too, she is a mortal after all. Also, you have to take into account there might be something in her genomic essay that has added to the decision to give her chemo.
We just don't know. What I do know is that the only thing harder than being treated for cancer is watching one's loved ones going through cancer and its treatment themselves. (And I say this having lost both my parents to cancer, one when I was still a teen). I feel for anyone who is the same position as William. Money and status doesn't buy everything or peace of mind, even at times like this. All you can do is hope for the best, and have all the support you and your loved ones need.