Oh Kathy, I am so very sorry. It is just a nightmare to be on the sidelines while our troubled adult kids behave in the fashion your difficult child is. You're surrounded by help, your therapist, her therapist, you're doing all the right things and I know from my own experience, that doesn't take the nagging fear and anxiety away from you.
I hope you are continuing to keep yourself in supportive environments, perhaps stepping up the support will work, that's what I did, until pretty much every single day, I was attending a 12 step group, or therapy or a parent group, or NAMI. I had to keep my brain occupied so I didn't let the fear drag me around.
I don't know if this will be helpful to you or not, but recently I have been watching a lot of Eckhart Tolle videos on YouTube. I find them extremely helpful for me to keep my mind in a peaceful place. I listen to his CD's in the car. I am becoming quite the devotee! But in any case, it is a means for me to stay centered, balanced and peaceful in the midst of regular life. When in a hurricane, as you are, what I always did was step up my own support. It made all the difference in the world for me.
It's so hard. We'll circle our wagons around you as we do.................Saying a prayer for your difficult child and you and husband...............sending warm hugs for you to find some peace................