She was obeying one of Nature's laws.

I think I promised long ago to tell you of the day when Grizel would strut no more.

Well, this is the day.
Observe her strutting for the last time.

It was very strange and touching to her to remember in the after years that she had once strutted, but it was still more strange and touching to Tommy.
She was like one overfilled with delight when she saw him.

How could she know that he was to strike her?
He did not speak.