The answer to your question is that her name is Renee Bowen, sister to Ryan, and daughter to Chief Bowen.
In the young adult mystery The Body of Christopher Creed, the character of Chief Bowen is the town's chief of police who is also ultimately assigned to the case of the disappearance of Christopher Creed. Of Chief Bowen's family, we know that he is married and has two children, Ryan and Renee. Both children show several characteristics of their father, such as their rough characters and their seemingly mean nature.
We later find out that both Ryan and Renee receive shocking news when they discover that their father, Chief Bowen, is cheating on their mother with Mrs. McDermott. Remember that the story is based on the gossip and mean-spirited tattle-telling that goes on in high schools where privilege is rampant.