I'm sorry that you're going through this I've had my sister send me threats but she received treatment years ago. You tried what you can do, and she's hurting your children and you, you said to this day... In this situation I would cut off all contact. She's an adult and there should be no excuse to act this way, she should realize what she is doing, she's not going to change. If she wants contact, expect an apology, respect, a healthy boundary and much more that your own family deserves.