How did she respond to that?! Are you thinking about her while with other FBs? Then it's a real problem.

I think the main issue is her taking this assumed 'he's my boyfriend' position. It's like she's saying 'Because i'm the alpha, I'm deciding that we're in a relationship. Also because i'm the alpha, I'm going to bang other(s) without telling you. If you put take back one of those things you should regain your self-respect, obviously the 2nd isn't worth trying to stop.

If you don't address it, how you going to feel when she's putting up pictures of you both on social media and tagging 'bae'? Would be game over.

Goodluck mate, glad to hear you're already working out this mini-mess already.