In "The River-Merchant's Wife: A Letter," we observe the wife remembering how she first fell in love with her husband, and how that love has survived his five-month absence. Even though we only get the wife's side of the story, we have no reason to assume that the love is not mutual. Still, for the wife, her love doesn't seem to have been immediate. Instead, she seems to have grown into loving her husband. She may have even resisted her role as wife at first. But who can blame her? She was fourteen! In the end, though, things are all candy and flowers, as the poem delivers a wallop of a love letter to her absent fella.
This poem says that love is not something that happens at first sight. It takes time to develop (like, a year of what sure sounds like an arranged marriage).
Boredom and isolation are as much a part of the speaker's expression of love for her husband as her affections for him are. (Sorry, guy.)