Dear Sunset Shimmer,
My old pupil. It has been so many years since I last saw you. Since you galloped away through the mirror. I must say, I never expected you to try to steal the Element of Magic. I never expected you would be depressed, let alone suicidal.
I knew I should have found a way to make sure you knew you were welcome back in Equestria. Perhaps if you knew that, you would have been able to return here to seek refuge from how you were being treated in the human world. I should have used the journal we had, but I feared you had thrown it out and didn't want another human to get my messages.
I am greatly shocked by what Twilight has told me of your suicide note. To be honest, I am frankly disgusted that the human versions of the bearers of the Elements of Harmony treated you so horribly. I used to think the human world was very similar to Equestria, but I was sadly mistaken. You should have come back to Equestria, where you would be
welcomed with open forelegs.
Your former mentor and friend,
Princess Celestia
And here we have Celestia, recognizing her mistakes and thinking that maybe if she had acted sooner Sunset could have lived if she just came back. She's trying to keep herself dignified in order to avoid the soul crushing weight she must be feeling.
This equation expresses how sad Tia is...
🍰+ + fire🦅 <
Hooves not forelegs
I think bringing Celestia's thoughts into the story says a lot about how everyone (or everypony in this case) was impacted by Sunset's decision to finish it all.
8544935
That would be the pony equivelant of saying 'welcome with open feet'.
Not very fair of Celestia to place all the blame on them like that, but she's hardly privy to all the facts either.