Your friend’s family is in serious denial. There is little you or your friend can do to pull them out of it. Sadly, their inability to cope with the situation could end in tragedy. These boys could end up in jail, in a hospital, or dead. You know that. Your friend knows that. But until her parents know it and act on it, things are unlikely to change.
But there is one thing your friend can do. I suggest that she locate a local meeting of Al-Anon. Al-Anon is an organization of family and friends of addicts. Members teach each other ways to cope and how they can be less affected by the behaviors of the addicted family member. Often when one member of a family starts going and gets stronger, other family members get interested. There’s no guarantee of that, of course. But it does often happen.
There are Al-Anon meetings in almost every city and town. Go to the Al-Anon website and look for information about a local meeting. Your doctor might also know where to refer you.
You are being a good friend to care so much. Please pass on that information. You might even find it helpful to go with her to some meetings.
I wish you well.