Blue Rose is spot-on. If you have witnessed this behavior with your own eyes, even that won't make a difference to an adult who chooses to remain in a bad situation, and I say this from my own personal experience of having remained in a horribly abusive relationship for nearly 15 years. Calling the hotline will, as Blue Rose stated, give you answers, options, and valuable information. You can also visit the website for the National Domestic Violence Hotline for checklists, options, etc. ndvh.org
Best wishes to you!