It's a handwritten message on a Marco Polo Ortigas Manila letter print. It wasn't posted on Dara's personal social media accounts but there's proof that it was written by Dara.
Dara writing the letter and handing it to her fanclub Parkers:
Parkers posting the letter and Dara's personal twitter account liking the tweet:
You can view the entire letter below:
[Thanks to everyone who sent this in.]