Nogi can channel her powers through any object, but her holy symbol gives her an extra boost of power.
Most undead are weak against Radiant (holy) energy and Maelstrom is no exception, thus her reason for avoiding Nogi's attacks. In the sixth panel (last panel in the middle row), Nogi hits with her empty left hand and did little damage (Taddin used Commander's Strike to give her an extra attack). Maelstrom let her guard down, thinking Nogi wasn't much of a threat and got hit with Radiant Smite.
Radiant Smite doesn't normally cause the target to go flying. We'll just call that artistic license.