Answer: Kylie
Why:
All 5 people have items that have illuminating objects. The cuts made were near those objects except for Kylie. She had shiny fake nails meaning it should've been near her hand not her cheek. It could be she had a hidden blade in her nail to cut herself and along with the others. She is also the reason for the lightbulb breaking as well. She placed some of her gum on the lightbulb probably when no one is looking. When you stick something on the surface of an old light bulb, you create a different temperature causing it prone to shatter. The evidence that she did it was her gum with her saliva and her nail with the blood of the people she attacked.
