I believe that IF probable cause is found to warrant the parent's snooping, then yes. If not, then it is a major violation of privacy that will result in the child's trust being lost. It can then be terribly difficult to regain that trust.
Think of if this way - is it ever okay for your partner to read your text messages? I mean yes, your child is a bit different, but morally there shouldn't be a difference.
Let the child live a normal teenage(assuming there) life. Being over-protective or sheltering the kid will raise just another "millennial" wimp. The same kind that crowd our welfare systems because they have no social skills and don't want to work for anything.