How does Jackson's use of adverbs to describe Mrs. Walpole's actions characterize her?

Mrs. Walpole carries out her wifely duties with diligence. It would seem, on the surface of things that she has bought into her role as housewife and mother. There is, however, a sense of underlying resentment. We can see this in, as you mention, the adverbs used to describe her actions. As she tries to get the kids out to school it is like "wading through molasses". She also looks at her full glass of milk "smugly". Her discourse with her husband is so routine and mundane that she recites "mechanically" what she does every day. Although Mrs. Walpole carries out her domestic duties, there is a definite sense of animosity in Jackson's narrative.