Here is how Moon Dancer decides to have Celestia pass a new law in Equestria Civil War.
(Siberian Overture - Captain America: Civil War plays)
(we see Moon Dancer reading something)
Moon Dancer: Secretly learned and developed a spell for the removal of ponies' cutie marks.
(She had no idea who sent the information)
Moon Dancer: Used said spell to remove ponies' cutie marks and lock them in cutie mark vault.
(her heart beat faster)
Moon Dancer: Discovered a time spell and used it to create different dystopian futures. And Twilight just forgave her! She did all these things, and she just forgave her?! I think it's time I wrote to the princess.
(she writes a letter)
(Equestria Civil War)