Heartbreaking. Poor little girl crying out for attention, begging for it hurts the most, and then being closed off behind a physical door and even more important, and an emotional door (to her mother).
Notice the little chuckle from the mother when the girl throws her backpack in the garbage. Ridicule is something children quickly identify, more than most parents give them credit for. I believe that contributes to the escalation. I wish the mother understood the consequences of her breakdown in communication with her daughter.
I wish I could give that little girl a hug.