In Chapter 6 of 'Nim's Island,' Nim avoids telling Alex Rover the truth about her father's whereabouts. Instead of explaining that her father is not currently with her and is likely lost at sea, she creates an illusion of normalcy. She doesn't want to burden Alex with her worries or the reality of her situation. This choice stems from a desire to protect both herself and Alex, as she believes that revealing her father's absence might change how Alex sees her or make Alex feel helpless.
Nim also grapples with the fear that if she tells Alex the truth, it may cause her to lose the friendship they are building. By withholding this information, Nim can maintain a sense of adventure and hope in her interactions with Alex, as well as keep the spirit of exploration alive in her isolated island life.
As readers, we can understand that Nim's decision highlights the theme of friendship and the complexities of communication, especially when dealing with difficult personal situations.