I'm not entirely sure as I haven't read it thoroughly, but usually there would be a protagonist, maybe a female character who is at the center of the story. There could also be a male character with whom she has a significant relationship, like a love interest or a friend who helps her in her journey.
Typically, in a novel like this, there might be a main character who is an outsider in some way. Maybe she has moved to a new place or is in a situation that makes her different from those around her. There could also be a mentor - like figure, someone older or more experienced who gives advice and guidance. And then there would likely be some antagonists, people or circumstances that create obstacles for the main character to overcome. Without reading the book specifically, it's hard to name exact characters, but these are common types of characters you might find in such a novel.
The main characters in 'sweetness in the belly novel' are probably complex individuals with their own backstories. There could be a young woman who is trying to find her place in the world. She might be on a journey of some sort, either geographical or emotional. There could also be characters from different social strata, like a poor beggar who has a heart of gold and helps the main character in unexpected ways, and a wealthy merchant who is initially cold - hearted but later changes due to the influence of the main character. However, this is all speculation without actually reading the novel.