The Shadow Fox

Nicola Pines is a seemingly ordinary girl who became the ward of her father's friend, Bruce Wayne, when she was six years old. Once she opens her mouth, you best be careful what comes out, because she is not fun when she's angry.
At dusk this black-haired, hazel-eyed girl becomes The Shadow Fox, the female protégée of Batman, and the only member of that team to have a power, though it's a power she loathes and rarely uses, due to it being the fact she became an orphan.
She was the apple of her guardian's eye for three years, until he took in a boy who had lost his parents to 'a very mean man.'
After that, he had no time for her, training the boy to one day take out that man who had killed his family.
In turn, Nicola began her own training, working harder than the Grayson boy in order to build up muscle and stamina, flexibility, speed, and strength. She chose a weapon and began to perfect it, hoping that when she did, she would gain his approval.
The tonfa proved a difficult weapon to master, but she worked extremely hard, refusing to give up even when she was advised to. The bruises she received from her training worried the other ward, and he followed her one night, watching as she began her intense training regime.
When he saw her pulled the tonfa from their box and saw how practiced she was with them, he could barely constrain his applause. Instead, he hurried back to bed and pretended as if he had never seen a thing.
The next night, he brought their guardian, and when he saw how skilled she had become in a few short months, he burst into the room, shocking the poor girl into nearly dropping her tonfa. He invited her to join their mission, which she gleefully accepted, on the condition her power would only be used when, and if, absolutely necessary.
Four years have passed, and the two young wards have become close friends, forming a strong, close bond. But when the bond is tested, will it it prove truly unbreakable?