I have no strong feelings about whether our fandom's grey pegasus makes her living as a mailmare, or whether she goes gallivanting around with a Doctor in a peculiar blue box. I don't mind at all the idea that she's a genius, or scatterbrained, or has an unhealthy obsession with muffins. I cast no vote on whether she lives alone or has a unicorn filly or even an adopted daughter on top of that.
For that matter, even though she'll always be Derpy to me, I harbor no resentment towards the name Ditzy.
I honestly love that there are so many interpretations of the character... after all, she's come to represent the many fans who love her, and those fans come in all varieties.
So thank you to all of the fans who carved out a bit of her personality in the countless creations that have been churned out. Everyone breathed a little bit of life into the cross-eyed mare, and something pretty special came from it.
As for Dinky, while I suspect that she was cast by fandom as Derpy's daughter for no reason other than a superficial resemblance, why not run with it? If some didn't want our pegasus to have to be alone, I can certainly support that sentiment. Everyone should have someone special in their lives... makes no difference who you are.
Besides, Luna had to be up to something for the year she was conspicuously absent following the pilot episodes. There was probably quite a backlog of pony wishes to clear from her in-box...