I mean, you can't save people from themselves.

At this point it's pretty clear. You've all set up this situation in such a way that she's going to be forced to pick between you.

You may not like who she picks. I've yet to find a good way to tell a friend that someone is wrong for them, much less some of the things you say. Maybe you've done all the right things, but I've seen this movie before. I know how it ends.

I can only say I wish you the best of luck in getting through to her. Because if she cuts you out of the wedding, make no mistake, there's no going back from that. If you've got a hail mary play, this may be the time to toss the dice.

At some point you may have to accept that she's not going to listen to you. You may risk alienating her by constantly telling her what is wrong with him. Rather than telling her about HIM, ask her about HER reactions to what he does. How does she feel when he does x, y, or z? How would she react if YOUR significant other did that stuff to YOU? She may feel compelled to defend him, so just telling her he's an a**hole isn't going to work. But getting her to think about how she feels about it might work. (Sorry, I don't know how I turned the BOLD on so I don't know how to turn it off!)

My family learned the hard way with my niece that when someone is in love with a person as well as the lifestyle that the person seems to promise them, that love is blind, deaf, and dumb. My niece fell in love or whatever with a much older man who already had kids from a previous marriage. He presented himself as being rich and he was handsome and well-mannered when I met him once, but my father was quickly skeptical of this guy due to his age and being divorced while my niece was just out of college and in her early 20s when she met him. My father doubted that he had the amount of money that he implied he had or that this guy was serious about ever marrying my niece. But her parents were quite taken with this guy for a while, until the engagement he said he wanted with her kept being postponed..

Long story short, my father was right and he turned out to be a bum and a fraud who really wasn't wealthy and he kept stringing my niece along about the engagement. So for a few years after she got out of college and turned down a job offer from a firm that would have put her thru grad school for an MBA on their dime, she spent those years instead traveling with this guy and living the high life off of her savings. He dumped her right after she ran out of money and after she had thrown away her whole undergrad degree and career chances. By this time her parents had already come around on this guy, but it was too late for even them to reach her. She is now living in Hawaii I hear and has little contact with her parents, who are ashamed of her and estranged from her as well. Too bad nobody like you, Lady A, had gotten medieval on this bum before she ruined her life. The silver lining is that at least she didn't get knocked up by this bum...

Maybe he's a member here

Wow. Hope i don't fall out with you

I'd suggest writing it down in a computer file when you talk to her - with a date on it. You might need to put events together one day to get help through authorities. (You know log it afterwards).
Usually folks in abusive relationships need an 'event' to get out of it.
I'd be surprised if him threatening your friendship isn't a small one.

I am dealing with a similar issue. A family member is involved with a very demanding POS. She always takes his side.
Her head is now full of misinterpretation, misunderstanding, and untruths about everything but what he wants her to do think.

I think he is a narcissist. I think she is in danger.

I recommend you start documenting your conversations. You will need such information when you ask the court for a restraining order, and reports to the police. Provide copies to others as precaution against fire.