Why is it imprtant for Sarah to tell Jacob that she wasn't mild mannered in her letter?

Sarah describes herself as strong, a hard worker and not particularly mild of manner. Or, in other words, very much a stereotypical Yankee woman from Maine. It is her response to a personal advertisement in the newspaper for a companion to the widowed Jacob who can take on the roles normally reserved for mother to his two children that brings her into the orbit of Jacob and his family.