Religious persecution
Judaism is forbidden in the New World where Esther finds herself. As her name suggests, she is a character for whom religious persecution has always been a part of life. Her parents were victims of religious persecution in the Spanish Inquisition, where Jews were made to cease their religious practices under threat of death. As Esther's stories suggest, being true to one's beliefs under duress is a scary but meaningful challenge.
Conservatism
In her own community, Esther was an outsider. Although her Judaism is presumably "far too Jewish" for New World Catholics, it was certainly not "Jewish enough" to spare her from the misogynistic ideas of her parents about marriage, and when they ship her off to Amsterdam to be married to some random guy who lives there, she decides to go her own way. This is a picture of how moral conservatism actually affects children; instead of abiding by the small view of the world they are offered by their parents, Esther explores the world freely.
Stories and meaning
Esther is a girl disguised as a boy who ends up being a story-teller. This is like the midrash tradition of Judaism, where old scriptural stories are recast in modern garb, and the stories are shown to be still applicable and meaningful, because Esther's story is very similar to her namesake from the book of Esther. When Esther tells stories, she isn't trying to capture something religious. She is being poetic, channeling her imagination into dazzling stories. She is participating in the game of human meaning by allowing her community to enjoy her mind and imagination.
