D14 has a lot of anger and she needs to release it, to get it out. Threatening OW’s life not a good idea. You need to get this back on track.
Thank H for informing you and assure him that you will deal with D14. Assure him, make sure he knows it, you don’t need police involved.
Next talk with D14. Tell her about MLC. Tell her how her Dad is dealing with some past trauma from his childhood, has changed, and is reliving a time from when his was damaged. Let her know that this hurt / damage from his last is significant, really a big event, usually some abuse or such form an authority figure. This lets her know that she is not destined to experience her Dad’s slip into the abyss.
It also doesn’t hurt to let her know that for the most part Dad’s behaviour is beyond his control. He did try to contain it for a while, but eventually his crisis becomes so great that he explodes and destroys himself and quite a few around him. He is running from his pain, and OW is just a distraction.
People have a need to understand something before they can move on or let go - children are no different.
I would also explain that OW is “usually” a damage person as well. D16 is correct, someone who goes after a married man with three kids - yeah, OW is not a nice person. She is damaged emotionally also.
Now, you can probably see D16 is projecting her anger towards Dad into OW. D16 will have enough anger for OW, all on OW’s merit and actions. And will get much more because D16 cannot risk losing her Dad.
Tell D14 it is ok to be angry, however talking to OW obviously doesn’t do any good. So, you and her need to find her a safe and proper outlet to release her anger. Something physical, sweat it out. Buy a punching bag, go for a run, join a gym, etc...
You and D14 sit down and together block OW on all social media. You can confirm to D14 that OW is what she is, that her views are correct, and D14 doesn’t need to associate with her - on a social platform. She is not her friend, so do not spend your time on her. Eventually she will see OW as just a hurt person, but not for a while
D14 can control only herself. A lesson you will want to pass along a some point. D14 cannot wake up Dad or OW - she only controls herself. She needs to see that, and be responsible for her actions.
Nyla, D14 is grieving. This is bargaining. She is attempting to change the outcome. A good thing. D14 is moving towards acceptance, even though she does not, and will not, see that yet. The bargaining stage is expected; everyone rebels against change, or attempts to bargain against it. She will traverse it. She just needs to realize their are lines she shouldn’t cross.
This is a big topic for you and your kids. The door has been flung open, make full affect of this opportunity. MLC is a horrible painful time, and an incredible opportunity for growth and understanding - even for a child. How you treat someone who is suffering, how you felt during this time and the realization that you do not want to ever make some else ever feel that, that you can only control you, and so on. Just a few examples. Children are thirsty sponges looking for knowledge. Some big life lessons are right there. Most people never look beyond all the pain.
You are blessed Nyla, you have compassion and can teach, show, at least three people how to live better instead of bitter.
This is where you focus. You and your kids.
DnJ
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.