Bea : Not standing still !

My favourite model of all time, my little niece Bea.

How does one make those critical adjustments in the split of a second ?

Small child of variable speed/acceleration and of no predictability whatsoever ... which shutter speed will blur the background and yet freeze her face ?

How do you change that setting in the fraction of time between her launching herself, and then hiding behind the nearest tree !?

Experience experience experience I guess ..... ?