There's a possibility this woman has/is developing dementia, in which case she should definitely be out of there. People with dementia can act out physically and cruelly. Barring that I can't see how anyone can say the contact was accidental. Her eyes are clearly focused where the kid is just before she knees him.
The object in her right hand was small. She could have easily rested her hand on his shoulder to make him aware of her presence. You can see that she does a little stutter step as if gearing up enough momentum to launch the child forward. Can't believe anyone would try to defend this.