Why does the leader of the "Little Sisters" dislike Jenna in the novel, Everything’s Eventual?

Jenna is the youngest of the Little Sisters in “The Little Sisters of Eluria.” Her mother tried to escape the cult, but she had to return because she became so sick outside the group. Jenna’s mother could not be saved, but the sisters nursed Jenna back to health. Mary, the leader of the sisters, doesn't like Jenna because she returned wearing dark bells. She dislikes her even more when she learns that Jenna is helping Roland.