Ah. Well that's probably... quite time-sensitive, isn't it. Ominous chanting either won't at any point do anything or should be assumed to be potentially about to do something in the next, like, thirty seconds, and they already know that their quarry is, in fact, magic.
On the bright side it also makes a noise which can cover up a small amount of whispered planning. "If it's a lot of zombies we're going to have to go straight for kill the spellcaster but... if it's just her, try to get her attention long enough I can... grab her or something?" he suggests.
He does really want to at least try talking to Gulnan before going straight to stabbing if he can potentially avoid it by simply clamping a hand over her face long enough to stop her encanting. If she's, like, a human sized woman not wearing a helmet and doesn't have quite a lot of combat training he should be able to do that, especially if he can catch her by surprise. The attempted murder via horrible wet zombies was not, like, awesome, as a sign of ability to make friends, but who among us has not done some fairly horrible murders in response to being kidnapped to be experimented on for our blood, amirite, he doesn't super know how necromancy works, they might just be intrinsically hostile creatures and not constitute a specific murder attempt.