really? shaking? how strong was this woman exactly
It was a 3 year old, they're not big.
When you shake someone severely, particularly a child, you're literally shaking their brain around the inside of their skull.
Their brain gets smashed by the skull protecting it, causing bleeding and brain damage.
When the shaking is over and the brain swells it pushes against the confines of the skull, putting pressure on itself and further causing damage.