Remember Celestia has a long Lifespan, so there must be a Human counterpart for Celestia for that entire Lifespan, there’s probable more older and younger versions in the world.
The same could also be applied for other characters… Think Link from the Zelda Franchise.
This isn’t Principal Celestia. It’s Princess Celestia during the events of Between Dark and Dawn. Her hair’s shorter because it’s in a ponytail. She snuck through.
It’s the exact same color scheme in the exact same arrangement, but her hair is shorter and her body smaller. Maybe Celestia having some kind of fountain of youth thing going will make her the final villain of the EQG series?