I designed this character last year and I liked her but she was missing something so I left her. So awhile back I picked up her design and drew it again but better and liked her a whole lot better!

So Eilwen was a regular human travelling with her parents. They were heading to pay homage to the new god of that forest. They did so. On their way back it came across them hurt and bloodied. In that moment it chose the daughter as a vessel and hid inside her body from its pursuers. It happened all in a flash leaving the family very confused.

They returned to their village some time later and remarked how strange that was.
The next week passed by and the daughter saw a flower growing from her tailbone and tore it off in a panicked fury.
It stayed alive and by the time they realised what had happened, horns began to grow in.

Her mother knew then that the god took refuge inside of her daughter and renamed her so she'd be more welcoming to the god. Her old name still waits for when Eilwen is able to revive the god.

I may redesign the god later and fix the story up some more.
Not sure if she's just waiting for the god to heal or if she's actively going to a healing spring to revive it.