Im not real sure about this but from what I gather - the addict needs family support (in a positive, constructive way) There will always be advice like - run for the hills, kick them out etc etc but I tend to think if we can find that way of not enabling them (supporting them with the addiction by just letting them know from a distance that there is a safe place/person to be there if they want to stop) it may help.
Does that make sense? Its easy to say ' just stop ' but when a person is so far into the addiction, some cant find that way out and they need family.
Im not by any means saying let her do drugs in the house until she 'sees the light' she needs to leave or want her life back. Sometimes when they go into rehab its like a 'relief or maybe this time'. We get some time out, I guess, hoping things will be different. Thing is though, most have this addiction all their life and if she truly isnt ready for it, not much will change.
Your bf sounds just like a parent who is hoping it will be this time too, can he realize that there may be many more 'hoping' times to come.