According to Mr. Dimmesdale, what admirable trait was shown by Hester's refusal to identify the father of the child?

Dimesdale was actually pretty damn relieved that Hester is such a strong woman,

She will not speak!" murmured Mr. Dimmesdale, who, leaning over the balcony, with his hand upon his heart, had awaited the result of his appeal. He now drew back with a long respiration. "Wondrous strength arid generosity of a woman's heart! She will not speak!"

He says that, although sinful, she certainly has heart!