Friendship can be a theme. For example, if Grace makes new friends in the story, it shows the importance of human connection. Also, perseverance can be a theme. Say Grace is trying to achieve something difficult in the story, like learning a new skill, and she doesn't give up. It shows that with hard work, one can succeed.
Love could be a theme. It could be love for family, if Grace has a story that involves her family in a loving way. Or it could be love for nature, if the story is about Grace exploring and enjoying the natural world around her. There are also themes like courage, where Grace might have to face her fears in the story.