Supernatural x supernatural!Reader

Daughter of Death. Friend of the Darkness. An angel. The angel. The hidden angel.
Always there in the background, you won't even notice it but she's there, writing down the history of the universe, observing and amusing herself.
She's a little younger than her father, nearly as old as God but equally as strong as Him. She takes up her father's work as Death when he's absent, sleeping or whatsoever.
But this was normal for her, too comfortable. So every once in a while, she turns herself into a mortal creature with no recollection of the fact if what she is and gets born into a selected family to enjoy the unpredictable universe till the mortal form dies and she returns to her father Death.
She could be anywhere. She could be anyone. She could be you!