Jumpin_Bean... asshole behavior or not... the facts are the facts... you can't control anyone... you can't convince them when they don't want to be convinced... and you cannot tell them how to run their relationship.
You're an outsider... which means you have to wait for your friend to either ask for your advice/perspective or finally admit you are right. Till then... all you can do is watch from the sidelines...
If you jump in and try to tell her what she needs to be doing... him and her both will turn on you. He will use the opportunity to get rid of you and she will feel betrayed by your lack of faith in her as a friend.
Either way it goes... you're powerless to help until she comes to you.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen