So I’ve just had a look through dd1’s phone and seen plenty of evidence. Have taken videos of the videos so there is absolutely no denying it. Suspected it for a while as discovered cigarette papers in her room. She is the master of denial and secretive. She is out a lot with friends/sleepovers although I always check everything above board with adults. We have had a rocky relationship over the last year and thought we had built bridges.
I did this stuff when I was older. My mum got really angry and hated me for it and it just alienated us and was counter productive and didn’t change anything. I don’t want to do the same thing with dd1. She has seemed happier and worked hard this term. She’s young though but she is very strong willed/independent/socially confident. She’s also a sweet kid at heart. Teens - why do they put us through the wringer?? 
What is the right response!!!