My Heart is Laughing. Book 2: Rose Lagercrantz

This is a story about Dani, who's always happy.
She's unhappy too, now and then, but she doesn't count those times.
But she does miss her best friend Ella who moved to another town. Since then no one is allowed to sit at Ella's desk. Otherwise where would Ella sit when she came back?
"Ella is not coming back," said the teacher.
"You never know," said Dani.
She's not one to give up hope, even when everything seems hopeless.