Yeah ok if its like really bad  for instance taking drugs like cocaine and heroine, yeah u should inform his/her dad. if she is like sleeping around with different guys and acting like American sluts definitely u should do that. but i didn't get what u were saying make it clear what bad stuff they are doing. if they are just drinking and smoking weeds and partying around and wearing tight short skirts i don't think that is bad. so u know make clear what u talking here about.