lucy has a sister?! and she's a what?!(a natsu x reader story)

ok lucy's sister who has been missing since lucy was five almost six appears and lucy is happy. lucy was also happy for what she became....a dragon slayer! but one question who was the dragon? what is her element? okay more than one but why did she run away at age four. yeah you heard me age four. simple the pain of losing her mother and neglect from her father was too powerful for her small heart to handle. now why does this concern you? well because you are this girl. you are (y/n) Heartfillia.