The Red Haired Devil

Kairi, daughter of red haired Shanks, was left with Luffy at the age of eight. Luffy's granddad decided he would make her a marine like he planned to with Luffy and Ace. He blamed Kairi's dad for Luffy wanting to be the Pirate King, but held no grudge against her, remembering Roger's words of a child bearing no sins.
Her and Luffy are left with Dadan to become stronger. Once she meets Ace, she's interested in why he's so mad. She decides to follow him and Luffy as Ace tried to lose Luffy. She finds his and Sabo's hideout and they begin question how she was able to follow him. They all grow really close until someone finds out about Kairi's true identity and Sabo's parents find out he's alive. They set out to sea to get away but are quickly blown up by one of the Celestial Dragons.
Dragon finds them and gets their wounds treated. Once they become better, they train and join the revolutionary army.