Valley was doing something to her friend, Arrow.

Arrow was crying as she stepped on his head, his mouth on the curb. This was known as "biting the curb." Valley is just traumatizing Bally while he was watching.

Arrow: M-MAKE IT S-STOP!! he cried

Valley: Just shut up, bitch. You deserved this. she said as he stomped on his head, making him scream and his jaw made a cracking sound.

Bally: watching in horror

Arrow's jaw bled against the sidewalk, as Valley smiled as Bally watched in horror..