Clarissa doesn't want to be rescued

I killed all the guards in the area, including the captain of the guard, but was unable to rescue Clarissa. I ran around the area to confirm that I had gotten them all, but to no avail.

I think this happened because I pulled all the guards away from the area using decoy totems. When I approached Clarissa after killing everyone, the quest text ("Kill all guards" or something to that effect) popped up. Because everyone was dead, I technically couldn't kill them, and thus, could not set the flag for quest completion.

The quest completed after I reset the instance and killed everyone again. It's worth noting that the quest text did not pop up this time.