Who is The Narrator's Wife from Welcome to the Monkey House and what is their importance?

The narrator's wife was married to the narrator when they were teens. She has a good sense of humor. When the narrator falls asleep in the bathtub, drunk, she covers him with bubble bath. She also knows how to make him sweat. The next day, she goes off alone and comes home late. She ultimately cares about him, though, forgiving him for his drunken debauchery quickly.