Marjorie Preston was a schoolmate of Lucy Pevensie. Anne Feathertone was jealous of her friendship with Lucy, and scolded Marjorie for the time she spent with her. Lucy overheard this conversation via Coriakin's Book of Incantations while voyaging with the crew of the Dawn Treader. Later Lucy regretted having heard the conversation due to the fact it ruined the relationship.
Aslan told Lucy Pevensie that Marjorie was
This suggests that Marjorie was an easily intimidated girl, but not mean-spirited as Lucy was quick to assume.