Opinions about the book I am writing?

Okay, so I'm writing this book about a girl named Julianna and her brother James. Julianna goes to a costume store and tries on a dress, which turns out to be magic and brings her back to medieval times, where her parents are King and Queen, making her and her brother Prince and Princess. When she gets there, she finds herself lost in a peasant area of the kingdom, where her brother finds her and takes her back to the castle. Her father, the king, thinks she ran away so as punishment she is sent to guard a prisoner in a tower. However, when she goes to guard him, she soon becomes his friend. She finds out that his name is Daniel and that he is actually innocent. His brother, who Daniel hates, committed the crime and framed Daniel. Then, the king decides that as punishment, Daniel should be executed and Princess Julianna has to decide between loyal to her family and royalty, or the life of an innocent friend. How do you think it should end? I don't want Daniel to die. Thanks!