What promise does Sophie ask Geoff to keep?

Sophie asks Geoff to keep her story about meeting Danny Casey a secret, hoping he won’t tell anyone else in the family or their friends. She shares her fantasy with him because she craves validation and wants to believe that someone, especially Geoff, might trust her story. By asking for his silence, Sophie is also seeking a bond of trust, hoping he’ll see her as someone who could have exciting experiences. This request reflects her desire to make her story feel real and to preserve the thrill of her imagined encounter without facing judgment or disbelief from others.

This question related to Chapter 8 English Flamingo Class 12th NCERT.
From the Chapter 8: Going Places.
Give answer according to your understanding.