Complex sentence: Lady Tremaine demands that Ella makes her head of the royal family and give her daughters proper husbands when she becomes queen and when she refuses, she smashes the shoe and locks Ella in her room.
Split into simpler sentences: Lady Tremaine demands that Ella makes her head of the royal family and give her daughters proper husbands when she becomes queen. When Ella refuses, Lady Tremaine smashes the shoe and locks Ella in her room.