My bff is acting werd?

she used to b a really good kid, a now she has a new bff and two nights ago she pierced her own ears without her parents knowing. She makes out with her boyfriend and she lets him touch her, if you know what mean. She is a very young teen. I dont want to talk to her about this because i dont want to get involved, and i dont kow how. My parents tell me to be careful with her. I am getting worried. What do i do. They said that if i hangout with her long enough, then i will start doing what she is doing. I doubt that. What do i do, she is starting to scare me. Please help. Thanks.