Yes - sometimes you need to be a little tougher - I am honest with her. It isn't like I sneak and read her stuff (whcn I did) - I told her I was going to - I also let her know I know kids will read some stuff and say swears and stuff like that - you are not going to get in trouble for that. I am reading it to make sure you are safe.
I did read some things I did not like. But I knew she was acting like a teen - I was only focused on ensuring she was not harming herself - she shared that with friends -some of which would go and let a trusted an adult know - some would not - I knew the friends that did without anyone telling me.
I could actually tell by the way she responded (non-verbally) that it did give her comfort that I was watching out for her.
She is just finishing up her junior year now. And has been progressively getting better. Less outbursts, being more open and talking with more about just what is going on in her life; she seems more content and comfortable with herself.
Every child is different and you adjust yourself to what best works for that child.