Riker shoots her three times. The first time, she goes stumbling back. The second time, she almost collapses in pain (and would have if she hadn't grabbed the table). And that was after a quick burst. A sustained burst would have Yuta on the floor in agony, unable to hurt Chorgan. But no, despite the fact Riker has a means of sending Yuta reeling, he chooses to kill her instead.