Best friends or maybe more

I have known this girl for years we first met at Primary School which was a very long time ago. and everyone says we should be together but she says we just friends but she does act strange a few times when I had a girlfriend here is what happened. So has you do you change your relationship status on Facebook to in a relationship I did that and this goes back to my friend who I’ve known for ages. She didn’t talk to me which was strange and my girlfriend said that my friend sent her a Facebook message saying that “I don’t love” her how can a best friend do that could she be jealous? most people say me & my best friend should go out together as we know each other a long time since Primary School she just says we friends It’s all confusing really best friends don’t say to their friends girlfriend that they don’t love them. She also tags me on a facebook status (every day) She also adds a picture of us together and tags me in it And the same thing happened when I went out with another girl my friend went in a mood again.

What do you think it could be? Thanks for reading 🙂