what do when your friendship is slowly slipping away?

my best friend has a boyfriend that i never talk to so it makes things awkward. I never see her without her boyfriend so i feel uncomfortable when i am around her because they always have their arms around each other and tickling each other.

We don't talk as much at school or text or call each other as much either. I miss her and i don't feel like i do not know her anymore. Also she has very different friends than me so i feel like i don't belong in her world. I feel out of place because i am not a fan of the other friends she has. I don't think their good people or a good influence but I'm scared to tell her that because i do not want to make her mad at me because she is my best friend and as bad as the friendship is now i still want to keep it.