concerned

While there are many reasons why a person would want to monitor the messages of a loved one, there are laws in place that prevent it without that person's knowledge because it is considered an invasion of privacy. Even if the person being monitored is a minor, their privacy is protected under those laws. There are services available that allow you to see a person's text messages, but they are going to get a notification that their activity can be seen. For example, you can look into our Digits features. You don't have to pay any extra in order to see her call logs and text messages, but setting it up requires confirmation from her phone number and once it is fully set up, she will get a notification that she is being monitored. 

https://www.t-mobile.com/support/plans-features/get-started-with-digits