Super kickass! I love it!
Seeing as how you already gave her OX tattoos and accessories, why not just say Oxblood is their surname to share? I like the idea of her being focused on family reputation or something, and the younger brother being the laid back goof often needing older sis here to wrassle their way out of trouble.
I suppose I feel like she doesn't really need OX tattoos *and* OX earrings *and* OX rings, especially if she's rough n' tumble and might find lots of jewelry getting in the way. Just my two bits.