Dear Princess Celestia,
I had a lovely time while you were gone. There's no need to thank me for arranging for some semblance of order while you were busy off in a hole under a dungeon under the surface of the Sun or wherever it is your sister put you while you were having that little spat. It was obvious from the moment I made myself known that you hadn't prepared your ponies for even a measly day or two of eternal darkness. Do they also scream and run about when there's an eclipse or a particularly large bird flies overhead?
You and I both know know that I could have done more. Consider it a token of goodwill that I merely had a bit of fun ordering your little ponies about and taking advantage of every amenity of your private suites. Where do you even find sheets with such a high thread count? Are they some kind of royal commission? It was like wrapping my naked body in a cloud, without all the cold and damp that comes with the real thing. And that bath of yours... one could fit at least five or six hefty stallions without even trying.
I had that secretary of yours pencil in some time for the nerds to start setting up all the legal nonsense. You're going to be changing everything to write your sister back into the government, so it's as convenient a time as any to lay the groundwork for unification. It would really be more convenient if you were an unabashed and unrepentant tyrant like me, instead of pretending to rule by law while intermittently editing history, but I suppose you're not competent enough to keep your ponies in order without the extra support.
If this goes well, perhaps we could even meet in person. Or maybe we already have? Are you entirely sure that none of the ponies in your court are actually me? I'm sure you understand that the temptation to laugh at your follies in person is immense, no matter how unwise it would be for me to, for example, take the place of your servants and arrange for a door to open to crowd of ponies at the precise moment you find yourself in a compromising position with your newly-returned sister.
Yours in future abutment,
Queen ChrysalisP.S. I took that horrid chimeric statue you keep in the gardens. There's a certain appealing repugnance about it. It will make a delightful decoration for my throne.