She lets him decide how long it lasts, and listens when he steps back.

"Better?" She asks it gently, taking the bowl and the butter just briefly enough to demonstrate how to cut the butter in - it's just a fancy term for mixing them together, breaking the butter into tiny bits and blending it until it makes little crumbs. "In what way?"

In asking, she offers it back to him, so that he has something to vent his frustrations on. With pie crust there's no such thing as crumbs too fine, and unless the speed generates too much heat, the butter won't lose its emulsification.