Died of sadness did make me wonder about something self inflicted.
"It usually appears after a significant stressor, either physical or emotional; when caused by the latter, the condition is sometimes called broken heart syndrome"
In any case if two relatively young people die in a short interval of time would be wise to look for environmental effects. Oil pigments have chemicals, and some colors were removed for being notoriously unsafe. Going further, slow poisoning to eliminate opponents with the benefits of plausible deniability is trendy among some criminals unfortunately. If somebody "dies of grief", research for discarding a hidden toxic should be started, just to be safe.
I also think that women have a harder time with this than men, possibly because maternal death in childbirth used to be so much more common. But this is just a guess. Certainly until it happens to you its not the sorts of things that you think about too much, and once it does happen you tend to speak to people who are going through the more acute phase of it since they are still actively processing it.
I have not dealt with such a change but have dealt with grief. Try to catch the sun rise. It is incredibly beautiful.
It will probably hurt because the instinct is to want to share the beauty to enjoy it. The good thing is that you can, with the version of your significant one you hold in your mind. I am serious, do catch the sun.
Grief hits in overpowering waves. Over time there is space between the waves. They will always be there but they become survivable.
All the best.