Other option to mention stoneskin/some plot stuff:
Finally, the mage-thief gets another chance to flex her might in the arena. And we promise her that there aren’t any pesky anti-magic ministers roaming the crowd, looking for errant mages to jail. Of course, even if there were, that might not be a problem for Imoen in this match. After all, Chelsea’s damage isn’t much better than Imoen’s! Of course, while Chelsea has no other skillset to speak of, Imoen has Stoneskin to immune the archer’s arrows, as well as Chaos and Domination to throws a few mental wrenches into Chelsea’s game plan.