"You know," he said, taking the pin out of his mouth, "a woman ought always to arrange her flowers before her glass." Miriam laughed.

She thought flowers ought to be pinned in one's dress without any care.

That Paul should take pains to fix her flowers for her was his whim.
He was rather offended at her laughter.
"Some women do--those who look decent," he said.
Miriam laughed again, but mirthlessly, to hear him thus mix her up with women in a general way.

From most men she would have ignored it.

But from him it hurt her.
He had nearly finished arranging the flowers when he heard his mother's footstep on the stairs.