Okay, they could be just different characters (like the Long Ranges and Croc Masters), but what about reconciling those backgrounds?
Maybe Onihashi lived in New Orleans for a while, married and had twin daughters, but some enemy of the Arashikage (maybe the Night Creepers) found Onihashi and he asked his wife to hide with the twins to not be trapped in the way of harm. Onihashi returned to Japan while his wife re-took her maiden name (Conda), escaped to Florida and raised the twins. Ann grew up as the "bad twin". Many, many years later, the twins went to Japan to meet their father, since Ann felt she was ready to take care of herself and dragged her sister with her. Onihashi trained the twins and gave them the labor of guardians of the Arashikage swords, with the shared name of "Vypra".
The twins never knew their father would die shortly after, commiting sepukku due to the betrayal of his disciple

When
Now, I don't know how to add her driving skills to the mix...