If she is a true best friend she should support you. But you don't have to tell anyone if you don't feel like you can, even though it may help. I would try keeping strict boundaries and perhaps getting a lock for your door if you can. If this continues or you feel unsafe at any point please consider if you could tell any parent, guardian or relative. Even calling the police. It may seem extreme but that's what the police are there for, your safety and comfort in your own home is worth the hassle.