But if the teen knows she can secretly appeal to keep the parents in the dark...
In order to appeal, she will have to go before a judge. I think that most teens would be mortified to have to go through that in order to have the luxury of engaging in irresponsible behavior.
There is a reason the abortion industry fights so hard against parental notification laws. They know that many of their potential customers will choose not to get pregnant if they have to tell their parents or go to a judge to get permission to abort a baby.