Responding to seeing the rampaging "Superman" on television, the remaining able-bodied Titans and Young Justice members (and Impulse, who is able to heal faster due to the Speed Force) confront the robot, thinking it to be Superman at first. When Lilith (who has met the real Superman before) cannot sense his thoughts, she approaches the robot, which breaks her neck, killing her instantly.
When the Titans and Young Justice saw the rampaging 'Superman' on TV, they confronted the robot, thinking it was actually Superman. However, Lilith, who had previously met the real Superman, couldn't sense his thoughts and approached the robot, which then killed her instantly by breaking her neck.