This one didn't surprise me, as too often a parent goes shortly after a child, as does a wife after her husband. Kim's Mother was gone 8 mos after her husband...
Then some go on forever it seems, less the other mate.
Yet, I've known a few too many couples, and parents with lost kids who do go shortly after each other. Yet, when one dabbles enough with numbers of those who do and don't pass early with a loss; many don't. I guess it's the impact beyond a broken heart literally that takes soul mates. A child is a soul mate of a parent, et al.
"Real Loss is when you lose someone you love more than yourself". Robin Williams
I'm sure Debbie felt this, RIP to a great actress...