Ok thank you, your advice was very helpful

Isn't it a bit too controling? I mean I want to allow her some privacy too and I don't want to be like a policeman who will check her phone whenever he wants.

Thank you for your comment. In the past I was asking her to show me the texts and she was overall more open about it, but she always disliked when I wanted to see them. If I ask for them now, I'm sure it wil turn into a fight.