I can't say what I would do or how I would feel in your situation because I have not been there. My daughter is not an adult yet. She's 14. It must be agonizing to be in the position you are in.
I will say, though, that one of the things I have learned over the past year is that trying to prevent an alcoholic from experiencing the consequences of their actions does them no good. It also made me crazy in the process. The more I tried to "help" my husband, the longer I prevented him from helping himself. When I finally let go, he helped himself. I know that it doesn't always go that way, but as long as they have someone to land on, they never hit bottom.
JMHO,
L