Info from WIKI

Hyeyeon was very friendly and seemingly got along well with her co-workers and students. She was shown to be very quiet and shy, often frozen in fear when the monsters attacked the gym. She was always concerned about the safety of the students, wondering what she should do to help, unlike Ms.Kim. She was also very noble, sacrificing herself in order to save Gyuhwan from Four's attack at the cost of her own life.