Kit, try not to visualize what your daughter is doing. I know my son has done some terrible things in his addiction too, and I refuse to give 5 minutes thought to it because it won't change anything and it will only make me sick.
My friends daughter was an addict from the time she was 16 until about 25, and she too sold herself for drugs. But she stopped, and turned her life around through hard work and a lot of therapy. She too married (a man who knew her past but "saw" her present) and has lived happily every after since.
These girls are our daughters, our sisters, our friends, and they don't want to be doing what they do. They are just lost in their addiction and hopefully one day will find their way back.
Keeping your daughter in my prayers, and you too, it's heart-breaking to be the mother of an addict.
Hugs