I suspect there is a lot of mixed feelings. The Queen already 'lost' her husband in a sense with the onset of dementia.
She has had to let go already. Grieve for a loss already. There can be a relief when one sees the loved one pass over, their suffering here is over, and if one has the sensibility, one does sense the radiant birth of the individual elsewhere. So life does go on, and all is well.
Henrik was at New Years and on vacation in Egypt when this happened. His dementia certainly wasn't very advanced. Its a bit cold hearted to think the queen said 'oh you are sick, you are dead to me' and started grieving already.
Its not a matter of not being sensible, its a matter of having to learn with the changing relationship with your partner of decades, while he slowly slips away from you. It certainly hasn't been years since he was ill, and she hasn't had time 'to make peace'.
Is dementia passed through the family? Is Price Frederik likely to develop it?
Dementia has different causes. Certain types, like that caused by Huntington's, is inherited. When it comes to alzheimers, only usually early on set form is inherited, but that is a rare form. If you have alzeimers in the family, you do have a slightly elevated risk for it.
Even if there isn't a long history, sadly it starts some where. My Nana died from early on set dementia. My Uncle, my dad's oldest brother, is now suffering from it. My father and his brothers all thought they avoided the family curse (until them every man on their father's side had a massive heart attack before 61, even in the extended family. My grandfather and his 2 brothers who reached adulthood all did. My grandfather and his eldest brother died of it. His younger brother is alive and healthy, works at 85, but did survive 2 massive heart attacks. Went to a family reunion in North Dakota, met the living descendents of my great-great grandparents. There was only 1 living man over 70 there, my dad's uncle wasn't there). Unfortunately my Uncle had a massive one at 68, and while he survived, dementia set in soon after. And while my father has escaped both, he was diagnosed 2 years ago with multiple myeloma. My youngest Uncle (dad is middle) faces losing both his older brothers likely in the next 2-3 years. My sister and I know while my dad has not suffered dementia, it is now known in our tree.