re: Apparently 18 year old Betty was truly destitute.

If you really want to help these people (and unless they want help it's almost useless) you have to take extreme measures.

Take them to an isolated, structured environment away from their territory. Cut off their contact with all but a few monitored people. Feed them well, and ensure no drugs get in. Have a good positive program and support system.

I mean, rehab, but good rehab. Long term. And then you have to release those who are just on streets into a new environment where they have a stable system, a job, positive influences and encouragement to stay sober.