How do I tell my Best Friend that her boyfriend is controlling?

My best friend,Madison,of five years has started dating this guy named Trent. She has been with him for 5 months now and she has changed dramatically. I'm pretty sure it's because of her boyfriend. Her boyfriend won't let her hang out with ANY guys except him. Her boyfriend doesn't like me so he has banned her from talking to me (and she has agreed)(She occasionally talks to me when he isn't around), he texts her 24/7 and he always has to know where she's at. And my friend told me in secret, that he physically abuses her. And she says she is still in total amor with him. I want her to get out of the relationship for her sake not mine. But if I bring it up she just says I'm jealous. I need serious help guys...any ideas?