It's a fake, badly recolored from official image of Kiara

It's been updated on the site that it was fan-made with someone's OC

It's likely a very rough version for the cover that the actual publishers (or author?) did
Just going by how the corner says "cover not final"; if this was a fan version it'd probably just be written below, not put in the image like that
It's likely whoever did the rough draft was just drawing from memory and not paying attention to the colours or design of Kiara, which is who I think it's supposed to be since the story revolves around her

I do believe that might have been a placeholder cover... but it does look a lot like a fanart. The episode is a Kiara-themed one, so it was probably supposed to be Kiara.

The finalized cover looks SO much better though, and the episode actually is decently good.

Hope that helps!

- Juuchan17

reserch says its a fake cover made by a fan but nobody seems to know