Martial arts theory wise, she's obviously strong, probably only one level below ZSF. However, as a fighter, I doubt she amounted to much, compared to her dad and the likes. Due to her connections, I doubt anyone in Jianghu would one to mess with her and she's typically not drawn to the seedy places anyway. Therefore, she wouldn't have much of a chance to fight anyone. Also, the only worthy opponent during her roaming years would be ZSF anyway, if she ever aspires to be Great-level. This is apparent as during HSDS, we didn't hear one story about her martial arts feats, even from her own disciples.
If I had to rank GX's fighting ability, it would be on par with her mom and below Xiaolongnu.