sickatheart,
I am so heartsick for you, and wish there was something I could do or say to fix it all.
Unfortunately, there is nothing you can do, or say, that can make her do what you think is best for her, including getting rid of her slug of a BF.
Maybe she will decide that she wants rehab, and will come home, we can only hope.
I would try to get to some meetings to gain some stength and support from others.
Hugs and prayers for you, and your daughter.