I´ve been in her situation, but wasn´t legally married, but common law. I went in to the station, after our break up and talked to his sergent and told him what had been going on, but there was little else I could do. I never took pictures of the bruises, or laid a complaint at the time. I was too embarrassed. I have no idea what happened to him. I got some feed back from friends who saw him. They gave me the indication the he´d never see a higher rank or get much work other than traffic duty. They understood he couldn´t be trusted, but couldn´t prove enough to throw him off the force. (This all happened in New Zealand… I know he hooked up with an even younger girl and I felt so bad for her. Just a clueless wide eyed puppy, she was.)
Not like it was an easy secret to hide. The people at my work saw bruises around my neck once and a black eye another time, close to the break up. They also saw the results of his controlling nature. I wasn´t allowed to have a bank account of my own, even though I had a job and my own income. I wasn´t allowed to go out with friends without him. Young and stupid, I was.
My advice is to document everything. Take pictures of things he´s broken and keep copies of anything he writes of a hateful nature. If he hurts you, make sure you get witnesses and pictures.
Get away from him. I know, easier said than done, but you will feel like an anchor has been cut from your neck.