The List of Real Things by Sarah Moore Fitzgerald

A poignant and big-hearted story about love, loss and believing in the magic of the imagination. The fourth novel from bestselling Waterstones Children's Book Prize shortlisted author Sarah Moore Fitzgerald, following BACK TO BLACKBRICK, THE APPLE TART OF HOPE and A VERY GOOD CHANCE.
Grace knows the difference between what's real and the strange ideas that float around in her little sister's mind. Their parents died - that's real. A secret hotel on the cliff-top where their parents are waiting - definitely NOT real. So when grief strikes again, Grace is determined not to let her sister's outlandish imagination spiral out of control. But the line between truth and fantasy is more complicated than it seems...