I'm sorry that you're going through this with your daughter. I can tell you that if I were in your shoes, I would be struggling as you are. However, the posters on this thread have given you sound advice. Your attempts to "talk some sense" into either your daughter or her boyfriend will only push her further away. My last comment isn't to suggest that you're treating your daughter disrespectfully in the manner you are trying to get her to understand the dangers, only that any method you choose will likely fall on deaf ears, or worse, push her further away.

It's not easy to sit by when you see her living with someone that you think is "bad news". It is my understanding that many people her age move between wanting more freedom and more security. Don't be surprised that if you let her make her own decisions (and mistakes), that she'll change her mind and return to you and your wife.

I have a good friend that I've known all my life. When she was 19-20, both she and her younger sister rebelled against their parents. Her parents were a little older than usual, in their early 60s. The parents were strict Catholics and wouldn't allow them to use alcohol or marijuana (or worse) in the house, wouldn't allow boyfriends to sleep over, etc. The sisters both decided to move out because "they were adults" and wanted to do what they wanted, and not abide their parents' rules. After less than a year on their own, and seeing some of their friends overdose, or go to jail, or whatever, they both decided to go back home to their parents. They had also struggled financially, underestimating how expensive it was to live on their own. They ended up with wonderful relationships with their parents.

BH (me) 50, WxW 47
Married 1994
D-day, plan A, & exposure Jan 2017
Divorced Nov 2017