She was once Mr. B's girlfriend; in fact, they were almost married, but things fell apart when Mr. B realized Sally's mom was playing some tricks to try to bring about the match (and he really doesn't like tricks . . . when they are against him, that is). And then things kind of blew up further when Sally got pregnant with Mr. B's child.
She ended up being okay, though: She made sure her daughter, Miss Goodwin, would be well cared for, and then she hightailed it to Jamaica, where she presented herself as a widow and ended up remarrying.