Help me find this movie

All i remember is watching a tiktok on it. There'a this girl with blonde/brown hair in a blue and white uniform who is being investigated because she killed her classmate who is also her dormate. All i remember was the girl confessing to her crime while her mother tries to stop her, and apparently she stabbed the classmate with a pen and then pushed her down something (most probably a cruise). I also know that the girl takes a drug to keep her awake and able to study better just to surpass her roommate in terms of grades.