I think Mara Jade wins. It depends how badly she wins though. In the ROTS novelization, it says Grievous was extremely fast, and the strikes were like 16 per-second, and the only reason why Obi-Wan won was because he was a Soresou master. However, the Clone Wars show that Grievous was pretty much wounded and weaker. It really depends if she's fighting the novel version or the movie one 😬