Hashem tests everyone! Nisyonos don’t just befall poor families. These things happen to ALL types of families and OTD happens even in homes of Roshei Yeshivas and prominent Rabbonim.
As PBA said no one knows what happens behind closed doors. And know one knows what happened with this child in her school, or within her tight circle of friends. She might have been bullied, she might have been made fun of. She might not have kept up with the class and fell behind and made to feel inadequate and stupid. Kids who lose their self confidence and self-esteem and whose teachers cut them off at the knees instead of help them find their way do tremendous harm without giving it a thought.
Kids who either have a problem at home or a problem at school but do not feel they have someone to turn to carry a burden within, a pain so large that it bursts until they lose their way. In trying to run away from the pain they try to run away from who they are and religion is the first thing they run away from. Because basically that is who they are. In addition, if its was a religious person that hurt them they blame the religion because it is all a jumble in their souls. “How could a religious person do that to me? What does religion truly mean?” They start to question G-d and have a fight with him. So if I stop davening what will you do to me? What did you do to that person that hurt me? And so on and so forth. They expect an immediate response and when they don’t get it they keep testing, they keep going. They are hurting and so they lash out. Once it starts to come out the damn has been broken. The pain they have been holding in side just comes flooding out in many different ways.
You can’t blame the child because you have no clue what happened to her/him. Were they molested? Were they humiliated? Is it a dysfunctional home that they just can’t handle anymore? Did the school throw them out for a minor infraction instead of work with them and show them love? If you don’t know the child and don’t know the pain they carry how could you possibly comment?