Enid Blyton 
The Mystery of the Vanished Prince [EPUB ebook] 

“I haven’t liked these holidays one bit, ” said Bets, dolefully, to Pip. “No Larry, no Daisy, no Fatty—a real waste of summer holidays!”
“Well, you’ve had me, ” said Pip. “Haven’t I taken you for bike-rides and picnics and things?”
“Yes—but only because Mother said you were to, ” said Bets, still gloomy. “I mean—you had to do it because Mother kept saying I’d be lonely. It was nice of you—but I did know you were doing it because it was your duty, or something like that.”
“I think you’re very ungrateful, ” said Pip, in a huff.
Bets sighed. “There you are—in a huff again already, Pip! I do, do wish the others were here. It’s the first hols that every one but us have been away.”