Attending a Harrowing is not a popular duty. Ninety-five percent of the time, you just sit and wait for hours for nothing to come of it. But you can't doze through it, because there is always the possibility that the mage will come back possessed, and the templars will need to act swiftly to deal with the threat. Still, that doesn't happen often. It's all tension and no release.
Briony fought her way into attending this particular Harrowing, however, because Lys Amell is not a popular person with some at this Circle. Unpopular enough, in fact, that there was muttering that she shouldn't survive her Harrowing. Nothing loud, nothing actionable, nothing she could take to Ser Greagoir and have him do something about. But enough that she wanted to be here to ensure the outcome in person. Briony's blade is the one at Lys's neck, and it will be Briony who acts, or no one will. She will ensure it.
For now, she waits. Until Lys returns to the waking world.