@Mia-Clarke It's good to remember that you don't need to (and most of the time it's best NOT to) tell the whole story on the cover. You just want to pique their interest, so they'll pick it up & read it.
I like your character design for the girl & the magical effect on the title.
It sounds like the tortoise is part of a deus ex machina (but at least there's the foreshadowing of the girl having similar traits), so that's something I might not want to give away on the cover.
But then again — it might be nice for reptile lovers in a sea of dog books.
Maybe you could hide the tortoise among the lilies? It would be great to have it barely noticeable in the illustration, so it doesn't draw attention until they know the significance after reading that part of the story.
It sounds like you're getting a good start on breaking away. Good luck!