I am the mom of an addict son.
I guess I always fantazied about doing an intervention, but the real issue for me was "I had to be strong enough to set my boundaries (no contact, no money, no food from me, no bus fare from me, etc.) and stick to them." The truth - I wasn't that strong. So although an intervention sounded great it wouldn't have worked.
So, I attend NarAnon and AlAnon, read alot here and post when it strikes me and am trying to get strong and recover myself from my codependency. I love my son more than I can express but I don't do him any favors by being his enabler.
Good luck and my prayers go out to you and your daughter.