Know that you have done the best that you can in both of these situations. There are times when we can't do it all. There are some people that have to step up for themselves and take action. You have given good advice and you have tried your best. Your first story makes me very angry because as a police officer he should not be harrassing this girl. And I can see where she is afraid to persue this, but she needs to.
The second one, well, I go with Jamie's reply. Call somebody. But I know that you don't want to make it worse for this teenager.
Remember you are only human. You can be there for people but you can't fix everything. Know that you are a good person for caring.
Hugs, Karen