Mrs. Hale doesn't do a whole lot in this book other than complain. Like her husband, she mostly just puts pressure on her daughter Margaret to fix the family's problems and to take care of everything. Her health has never been good. But the narrator also gives us the sense that she's a woman who isn't happy unless everything is going her way. As we find out early on, she decides not to go to her niece's wedding because she "had been detained at home by a multitude of half-reasons, none of which anybody fully understood, except Mr. Hale, who was perfectly aware that all his arguments in favour of a grey satin gown, which was midway between oldness and newness, had proved unavailing" (2.1). In other words, Mrs. Hale will miss a family wedding because she's not happy with what she has to wear.
Mrs. Hale comes from a wealthy family and never lets a day go by without complaining about how she married for love instead of money. Talk about shallow. That being said, she does have a deep love for her family, especially for her exiled son, Frederick. It's when she thinks about him that Mrs. Hale's best qualities really shine through. At one point, she talks about Frederick's mutiny in the navy and says, "I am glad of it—I am prouder of Frederick standing up against injustice, than if he had been simply a good officer" (1.14.14). When she reaches her deathbed, there is nothing she wants more in life than to see her son again, crying, "Frederick! Frederick! Come to me. I am dying. Little first-born child, come to me once again!" (1.16.41).
No doubt about it, Mrs. Hale isn't the biggest help to Margaret… or to her husband. But there's definitely enough love and goodness in her to get our sympathy, just like there is with Mr. Hale. After all, Elizabeth Gaskell always wants us to have sympathy for the weak, no matter how annoyed we might sometimes get with them.