She burnt them to kill them off,plus they had used Remnant on themselves to give themselves immortality and if she hadn't burned them,they would make another virus and got her park shut down. She burt Sunny to set him free from the Animatronic cat he had possessed. Rosie had made that cat in honor of him and if he ever had to have a physical form again. Now,for the reason she spared Glitchtrap. Remember that she said 2 people were going straight to the boiler room of hell? Glitchtrap was one of them. She had made a game for him and only him to play, One week at Rosie's UCN. It had included the Animatronics he had hurt the most. He was to suffer for as long as Rosie saw fit. And that would be till the end of her days. Rosie had made a promise,and when she does,she keeps them.