According to wikipedia, their society shunned them because they both feed off and project the emotions they feel. She didn't really grow up on Zeltros with her own species outside of her mother. Maybe the Sith Lord was just desperate. Or really wanted a hot apprentice.

EDIT; Never really imagined her as a fighter anyway. More of a manipulator/loremaster kind of Sith, as opposed to an 'UNLIMITED POWAAAAH' kind.