Daughter of the Storms
Percy Jackson rewrite where he has another best friend, a girl named Wilhelmina "Wilma" Kelly, who’s also a halfblood. She’s the daughter of Kymopolita, and similar to her mother she has a violent temper and control over storms. Her father is a meteorologist who studies ocean storms, and has always found them fascinating and beautiful. That’s what drew Kymopolita to him and led to the birth of their daughter.
Wilma is nearly a match for Percy in terms of raw power with her abilities but lacks control. They come easier to her though. They train together, Percy teaching her control and she helping Percy unlock his more destructive powers, like earth shaker abilities.
Wilma has black hair and dark blue eyes, and is fairly short. She uses a Kopis and an ancient bashing shield, and has a very direct and aggressive fighting style.