Yevette is a Jamaican woman who is being held with Little Bee in Black Hill Immigration Removal Center. We don't learn Yevette's story, but we know that the parts of her body that are visible are covered in scars, suggesting she's been through hell.
Yvette has sex with a Black Hill Immigration Removal Center employee in exchange for him putting a mark next to her name in the computer, showing her as set for release. In order to keep Yevette's release from looking suspicious, the employee selects three other girls at random to be released as well. One of those girls, of course, is Little Bee.
Yevette is a fun, straightforward character, but she disappears from the novel after the third chapter, when Little Bee sets off on her own for Andrew and Sarah's house. Yevette is something of a device to explain Little Bee's release from detention, but she also presents another perspective on the immigrant experience. Definitely read the book so you can meet Yevette. She's a cool character we'd like to see more of.