Thank you so much for the practical advice. This is what I was seeking. He did walk away this last time and that worked well. We have a resource that we just went through about “parenting” with a young adult and I think that is helping. Making certain topics off limits is a great idea. That is what causes issues once in a while. Family counseling is my goal for us.That's a complicated situation, @Choosingjoy - a couple of things come to mind.
One would be - have you considered family therapy, for all four of you? I'm bringing it up because often, it's an excellent way for an entire household to go through a learning curve together, on improving communication and setting boundaries.
The concept of boundaries is often misunderstood. People tend to think that boundaries are rules that should be shared with other people, to tell them where they can and cannot "go" with us (in conversation, or in actions, etc.). And that when someone crosses one of our boundaries, they are breaking our rules, and we need to tell them our boundaries again, just louder this time. This never works - because ultimately, we cannot control anyone's behavior except our own. So expecting that people will adjust to our own rules is just unrealistic.
Instead - we set boundaries so that WE know what we're going to do when things are going in the wrong direction.
Like the case with your daughter and husband. She has strong non-verbal communication that she uses to show her displeasure:
I'm gonna guess she thinks this is her best option to shut down or redirect the conversation - which means, she is assuming that she's got no other option...she can't NOT sit down for that lecture when he tells her to. But she isn't going to shut off her feelings about it, so she'll make sure he knows she's displeased/disagrees with whatever he's saying.
That's just ONE way to go about this. By 'healthy adult' I think you mean 'loving parent' - because if your daughter did this to a manager at a job, or to a cop during a traffic stop, or any other scenario outside the family? She would not be owed any grace and love, not at the age of 18.
So, your way is to go gently with her. Nothing wrong with that - but can you see how the scenario is doomed from the outset?
There are plenty of ways to construct some guidelines - boundaries - around how parenting is going to work, between her, your husband, and you. But she would need to be willing to dig a bit more into what she'd like parenting to look like, now that she's older. I doubt she could place a boundary that neither you nor your husband is allowed to require her attention; that she will walk away whenever she doesn't want to hear what you're saying. But maybe, she wants some topics to be off-limits? Or maybe, she wants to know in advance and have a time set for the conversation, so she's not blindsided?
Your husband sees her sighing or rolling her eyes, and he thinks he needs to parent harder and louder. Which of course isn't working. But I don't think it's wrong for him to want her to be willing to listen. So, while you all are trying to sort this out - he may need a boundary for himself, that says "when she rolls her eyes at me, I'll end the conversation, instead of blowing up. I'll walk away from it - because I can't change that behavior of hers all on my own."
But still - there will need to be a place/time where you all can get help with the core issue, which is: How to relate to your kid when they've become a young adult, but are still under the roof, and under our care?"
PTSD will make things more challenging for your husband, because his reactivity will naturally be rather high. But it's still about parenting, not PTSD (IMO).