Perhaps we could use a separate thread for the "whatever became of Della?" plotline. I will start it off by mentioning a reference to Della in the latest issue of the comic book DuckTales, #9. Second story, The Frightful Family Fishing Trip!, p. 2, panel 2.
Donald is complaining about Scrooge taking the family on dangerous adventures.
Donald: And I say you're just pretending things are how they used to be--with Della! But look at what happened to her!
Scrooge: Don't you dare mention Della, Donald!
Donald: I dare, Uncle!
Next panel, Beakley interrupts and ends the Della conversation.
The art shows that the kids have moved away from Donald and Scrooge before the Della conversation takes place.
Makes you wonder what happened to Della? Did she died and happened to her husband?
It seems that she didn't have a husband in this version of the Duck universe. They haven't mentioned one, anyway, which makes me think that she was a single mother. She probably didn't die, though. Seems too sad a conclusion to the "Della arc".