Why are you saying that? Come on, this is just one of their final obstacles. It has been one of my predictions TBH. Even though I thought it would be an enemy taking her blood. Be glad it happens NOW, and not in 8x16. Your reaction is EXACTLY what the writers want. The "will they or won't they" feeling. It's a pattern of storytelling. My guesses:
-Damon will still get the cure somehow. Either this one, or perhaps someone secretly brought the 1903 one (before the prison world disappeared).
-Everything supernatural will disappear, and everyone will become human.
-Some other twist.

I think Delena is pretty safe, considering the fact they've been through hell since 6x22. If anyone deserves happiness, it's them.

And again: I don't trust those leaked "spoilers." And even if it does happen. So what? Daroline danced in S8 as well.