Complex sentence: The enamoured Sibyl calls him "Prince Charming", and swoons with the happiness of being loved, but her protective brother, James, warns that if "Prince Charming" harms her, he will murder him.
Split into simpler sentences: The enamoured Sibyl calls him "Prince Charming", and swoons with the happiness of being loved. However, her protective brother James, warns that if "Prince Charming" harms her, he will murder him.