Dear Twilight Sparkle:
Ah, cutie marks. They tell you so much about their ponies, and they give us all something unique. It probably sucks to not have one, but then again, I've had mine for so long that I don't really know.
I'm kind of surprised by your mention of Apple Bloom. The last time you wrote about her, she seemed to be extremely advanced, with her desire to chase out the lower species when other ponies her age would be focused on playing with their Baby Horsie toys or having tea parties. Now, however, it seems that her “maturity” has given her an obsession with cutie marks which is slowly eating away at her intelligence. I believe it is called “Cutie Mark Desire Syndrome,” and not Down Syndrome.
But I digress. Your failure in getting young Apple Bloom a cutie mark in slave labor shows that you are unfit for the slave trade. That's one career option you won't be able to make!
On the other hoof, this Diamond Tiara pony sounds like she could grow up to be great if you took her under your wing. If you wish to complain about how she's not a unicorn, you could always invest in giving her a horn transplant!
Also, I'd like you to know that I am interested in knowing what these three fillies have planned. It must certainly be interesting if you think it will cause disasters. I would give you advice on how to deal with the impending calamities, but then again, it's Ponyville's problem, not Canterlot's.
Your thoroughly unconcerned ruler, Princess Celestia.