If he immediately dismisses your concerns and accuses you of jealousy then he doesn't sound like a great boyfriend.

I wonder how long she's been in the friendzone

If you can see yourself marrying him then get proof and show it to him. if you can't imagine spending the rest of your life with him, then save yourself the trouble of dealing with his psycho friend and end things with him

Don't give in to the threat.

You have two options....... If youve been together for only a little bit i would stand my ground. She may be crazy but you gotta out crazy her. If youve been together for a while i would question the relationship since he didnt take your concern to light and was so dismissive about what happened.

Not to be that person, but most of the advice on here won't work in this situation. Even with documented proof, he will turn a blind eye out of loyalty or what have you. For your sanity, walk out. Trust me, I've been there. It's *not* worth your time or your heart.

Maybe said friend should have just grown a pair of ******* and asked him out before he entered into a relationship with you, hmm?

Huge red flag! Run for the hills girl because it will only get worse from there

Sounds like a scene straight from Investigation Discovery. The poor girlfriend always seem to end up dead. ...RUNNNNNN

^ thats my failed attempt at humor. = FML, seriously