Once she is 18, you can treat her as an adult and if she threatens you , you call the cops and give her legal consequences.  You need to have firm boundaries for you and your home.  

You make it clear to her father that her drama is not welcomed in your home, he has any visits with her away from your home.  You turn your home into a sanctuary of peace and harmony, a safe haven.  

Once you have a semblance of a fortress built around your life, then you can let your guard down and relax a bit.  That's what I had to do.  

You also might want to consider some short term therapy to help you do this.  You need to know you have someone on your side, even if its a paid therapist.  

You can over come this, but it will leave you a changed person.  A wiser one and more understanding person when you come across another victim of stephell crazy.  

What does DH do about these emails? Why hasn't he told SD to knock it off, he doesn't want to hear it? And if he has, he should set filters to catch her emails and send them to junk or another folder.

He's allowing this to happen to you.

no email in bed. 

I know what it's like to be targeted, triangulated against, and to be the victim of relational aggression. I also know what it's like to have a passive, scaredy cat H who wouldn't protect me when his female relatives were blaming me for stuff that was his fault.

I want to give you a big hug and tell you "It gets better!"  Right now you're worn down, feeling insecure and unsupported BUT, you've found this site and the source of your strife is out of your house so things are already in motion to improve.

You're at the beginning of a new you, and while you're wobbly-kneed and weak at the moment, if you focus on self care and stick to the path of disengagement, you'll get stronger, healthier, and wiser. 

So much of the poo isn't even about you, but rather about divorce and poor parenting. It isn't personal - any woman your H partnered with would be targeted. Dysfunctional skids are just horrendous between 16 and... whenever they shut their gobs. It's like they're stuck in a loop of drama and vitriol, and stepparents make an easy target. By the time my YSD ran off at 19,  I was much where you are. But I hadn't yet achieved clarity, and it took a similar go round with OSD several years later before I hit the wall and realized that I had to change myself if things were to get better.

In order for you to heal, you need to feel safe. This means you need to have a convo with your H about his duty to keep toxic stuff away from you. Explain that you are trying to heal and need him to keep all things SD away from you, including reading her emails in bed (idiot!). Please do get a therapist, too; someone who will be on your side and support you as you recover from the constant onslaught of strife and toxicity. Be selfish for a while and focus solely on yourself, doing things you enjoy and creating happy positive vibes for you alone. Branch out socially, and invest your time in endeavors that will replenish your depleted soul. Too often we over invest in our steplife at the cost of other aspects of life, so it's all about finding balance through validation and affirmation that isn't predicated on whether some damaged skid likes us or not.

Lastly, be patient with yourself and give yourself plenty of time. Changing, recovering, rebuilding - it all takes lots of time. It's a journey of self to disengage well. Your H may or may not be supportive, but you have to prioritize yourself, because no one else has been. Refusing to participate in the drama creates a bubble of peace around you, and over time the bubble widens. My DH at some point accepted that I wasn't going back to the crazy and also disengaged. I deal with my people, and he (barely) deals with his. Our life is different, but far healthier and our marriage just happened to get stronger. However make no mistake - disengagement is foremost about self care, and I was focused on that rather than fixing our marriage.

Toxic feral Eldest would tell her mother Toxic Troll, lies and horrible things about me, Toxic Troll in turn would text these things to DH. And around and around we went.

DH now realizes that he doesnt want this toxic sludge in his life. I think it took Feral Eldest accusing him of abuse to really show him how far gone she actually was.

Its a horrible thing to be the target of so much poison. It hurts and it festers, and drags us down daily.

When Feral decided to live somewhere else and went no contact that was the best thing ever. Then in November , when she was booted from her living place, she ended up at her mothers. So now they fight almost on a daily basis, put the youngest in the middle, and then end up BFF, for a short time - only to start again.

The thing is, Feral is polite to her father, I am no contact, and things are neutral at our place.