I think there is a possibile plot point that you should address in some form... While getting a formal audience with Cadence will take a year, a less formal letter written to Twilight would likely get to her in just a few days or weeks.
Even if universe Twilight has a staff to read her correspondence rather than doing it herself...(hmmm naaa Twilight would speed read happily through bags and bags of mail) if the include info about the likely inadation of new strange ponies from Earth popping up near ponyville, her letter would like draw Twilight attention.
While this seems the likely outcome... You may want to just explain why it wouldn't work. Perhaps there been a long term mail strike from CE to Equestria because of too many accidents caused by a certain gray mail pony?

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It might work and may or may not be written into the story already.

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Yes, I have to admit, I came to this website to read novels for a few days, and I have seen the author's gender recognition problem more than once.