Unknown to Kyle who just asked Sarah out on a date, Emily was watching them via the security cameras nearby the school, and listening in using the mini mic she placed on Kyle sometime ago. Kyle hunt only lets his guard down with his sister making it easier for her to plant such things.
The reason Emily did this was because she noticed that her brother was acting weird for the past few days. He acted especially weird when he heard that Carlo had returned. At first Emily thought he was just excited that he was finally relieved of the duty of protecting Lilitth. Since he kept on complaining that it was boring.
Still Emily who was good at discerning things felt something was off, not only that seeing as she was really close with her brother made her suspect that something had happened. Emily knew that if she asked her brother what was happening he would never answer properly, since he hasn't told her anything that meant he wanted to keep whatever this was a secret.