Light was reassured by Rodius that she could actually be serious here and fight like the boss was an intruder in the vault area, something she wasn't too happy about as she really didn't like 'showing' her more, slasher type fighting style. However, as she was getting ready to stab Rodius with one of her claws, an alarm sounded with one of the ESPERs coming to talk to Rodius, explaining why the alarm went off. Light knew it wasn't anything in the vault area, as none of her alarm spells went off, and she soon heard the reason for the alarm, an intruder! Rodius apologized to Light and said he was going to put the fight on hold, giving a message to have everyone gather in case Rodius couldn't talk this person down. 

Light decided to shadow Rodius, her void origins making her unsensable or unscyable so unless Rodius saw her or she made sound, she was effectively invisible and it'd be the same for the intruder. She'd watch Rodius as he interacted with this intruder, just in case he needed backup or a way to escape, but would otherwise stay out of sight.