A Delicate Situation: How Do You Tell a Friend They're in a Relationship with a Jerk

My girlfriend is in an abusive relationship.  I've tried talking to her.  Admittedly, I haven't been very supportive.  I've seen evidence of the abuse she takes from him.  There are photographs of ver bruised and scratched face after a particularly difficult day with him.  But she won't seek help.  She insists everything is fine.  That his behaviour is normal.  That it's her fault, not his.  It's in his nature.