That seems wrong to be honest. Think about when you were her age, if you would've like your mom nosey in your phone. Try talking to her and building good communication and a good relationship with her instead. If you have a good and healthy relationship this shouldn't be necessary.
Do not do that. If you monitor your child's phone, then your child will get mad at you, and hurt the relationship. Plus, if your child is interested in technology, they could probably uninstall the app or disable it.