I wept at this news, for him for having suffered so much, and for her having to have witnessed it all.
I have been in a similar situation, widowed younger than Kate. A couple of things people have said- one is that she'll get another book out of it. I hope she does. Writing it all down, putting it on paper, is a very therapeutic thing to do and one of the only places you can be truly honest in these situations. So often very ill and disabled people are hidden away, don't appear, that was not the case with Kate and although it pissed many people off, I think trying to hide Derek from the public would have been worse. I hope she does write that book and even makes money from it, because what she has been is to hell and back and it won't make up for it in the slightest.
The second is that people grieve for the loss of someone before they die, this is often said about people with dementia or with huge personality changes, brain damage and so on. I did not find this true for me. Whilst the person was with me, I could hug them, kiss them, talk to them (even if they couldn't always talk back). You do feel you have lost a lot, but not everything. Once they are gone, it's a lonely lonely place to be and being a glamorous TV presenter won't change that one bit, plus she has two teenagers to support mentally as well as physically.
I wouldn't wish this on my worst enemy and I'm glad he's at peace now.