Before they've fully adjusted to the darkness, and are aware via anything but the feel of earth under their hooves that the path has sloped downward a little, it has given way under them, some of the flora and some distressingly large rocks along with it. Clarity can't even teleport. It's too dark to see where she might be going.
Clarity notices she has a headache, heals it, and says, "Does anypony else's head kind of hurt?"
"Princess Celestia," she asks when she's done, "any chance we could all get a teleport back to Ponyville instead of walking through the forest again?"
And then they are all in the sunlit town square of Ponyville, and Celestia has sourced from somewhere or other one of those chariots and four pegasus chariot-drawers for her and Luna to stand in looking appropriately princessly.
Clarity sort of stands off at the margin of the festivities.
She's supposed to leave after the celebration, and has just remembered this fact.
"Why so glum, my faithful student?" inquires Celestia. "Aren't you excited to return to your studies in Canterlot, now that your quest is at an end?"
"Well - I don't plan to stop studying, wherever I am, but - I don't actually have any friends, back in Canterlot. And I made some here. I mean, maybe that was all show for the Elements, maybe they'd rather only be acquaintances for now, but - I like them."
"I like you too!" says Joy, passing by with a small plate of cherry chocolate truffles intermixed with medium-sized chunks of rose quartz.
"...Of course, Princess." Clarity always has paper. She floats a sheet of it and a pencil to Celestia.
"I, Princess Celestia," Princess Celestia says aloud as she writes, "hereby decree that the unicorn Clarity Bell shall be reassigned to take on a new mission for the land of Equestria: she will continue to study the magic of Friendship, and report to me on her findings from her new home - in Ponyville."
Presently, the princesses are drawn away together in their chariot to general cheering and whooping.
"There were plenty, last I checked! I'd offer you some of mine, but - quartz dust," he says, with a shrug and a smile.