Alot of guys hit women because the women are hitting them, verbally abusing them or throwing the keys to their car outside and goading them on, and they lose control of themselves. This is what it sounds like to be in the rhianna-chris brown affair. there is no way out of violence if you are violent. the only way to win is not to play the game.
In the later stages, she won't leave because her will is destroyed, and a violent line crossed, because once the guy threatens to kill her, it becomes almost impossible for her to leave.
I hope she does not continue to play the game with him. If they still love each other after they learn self control and conflict resolution, then they can get back together."