Technically this whole page is non-canon.
I’ve always been amused at “Kid” adventure stories (like Pokemon) where the characters behave like young adults (leaving home to follow their dreams) but are portrayed as children so the target audience can relate to them.

Clover is a young (and rash/irresponsible) woman on a trajectory towards evil.
I figured her age should be 18-21, and then got the idea that it would be funny to have her be slightly underage and have Heather magically age her up by one year.

However this joke needs to be non-canon as (1) Artemis is waiting for an opportunity to make a minor attack on Kith (remember when Artemis threatened to give Kith something to “tantrum about” and when Kith skipped out she added “I owe you Elf!”) and (2) Dionysus is waiting for his Witch Clover to be delivered to him, and (3) Kith may have someone pursuing her.

Or if you prefer, Heather’s spell just aged up the 3 of them without a year actually passing in the world outside their little group.

Although it’s not explicitly shown, Heather cast “Tempus Fugit” to make a year pass like nothng. (“Tempus Fugit” is Latin for “Time Flees”)

And just FYI, I wrote the story so that the Elves (both Kith and Ralf) play with the 4th wall long before I ever heard of Deadpool.