I am so sorry that you have viewed this ongoing drama and your heart is breaking.
I know how it feels to watch someone look like they are dying in front of you.
Certainly not give her refuge if she shows....either should any family member. She isn't sober and in control.
She is running to him. If those evil texts are being sent to you or your family then authorities should be contacted for a wellness check. I know you said they haven't been much help. Often authorities will see druggies as a lost cause.
At this point there is nothing else to do.....it is so difficult. Get as much support as you can in the meantime.