Sometimes they spiral into the abyss and destroy themselves. What you can't do is allow them to pull you and the kids down with them. You can't fix someone that doesn't want to be fixed. They have to fix themselves.
Focus on YOU and the kids and go on with your lives as if she doesn't exist. Keep contact to the most minimal you possibly can and ghost her. She either comes around and starts a very serious process of unscrewing her mind with professional help or you move on from her. Once she turned violent that's a game changer. You need to document that and keep the kids away from her as much as possible.
