Jackdaw didn't quiver in the face of Varus's anger. She didn't feel in the wrong, she was protecting herself. It didn't matter to her what Rennac purported to be able to do, the man had not yet gained the right, nor the trust to implement any changes to her. Even if Varus sided with him, she would not allow it to be made by him.
She did find it interesting when Rennac practically stormed out. Running away in the face of resistance didn't speak any more in his favor, at least that's what it looked like to her. Still, she did not falter from attention, waiting and focusing on Varus until he officially brought the meeting to an end. After that, it'd just be a matter of prepping herself for the mission.