Understood Betsy by Dorothy Canfield Fisher

Betsy's birthday was the ninth day of September, and the Necronsett Valley Fair is always held from the eighth to the twelfth. So it was decided that Betsy should celebrate her birthday by going up to Woodford, where the Fair was held. The Putneys weren't going that year, but the people on the next farm, the Wendells, said they could make room in their surrey for the two little girls; for, of course, Molly was going, too. In fact, she said the Fair was held partly to celebrate her being six years old. This would happen on the seventeenth of October. Molly insisted that that was plenty close enough to the ninth of September to be celebrated then. This made Betsy feel like laughing out, but observing that the Putneys only looked at each other with the faintest possible quirk in the corners of their serious mouths, she understood that they were afraid that Molly's feelings might be hurt if they laughed out loud. So Betsy tried to curve her young lips to the same kind and secret mirth.

And, I can't tell you why, this effort not to hurt Molly's feelings made her have a perfect spasm of love for Molly. She threw herself on her and gave her a great hug that tipped them both over on the couch on top of Shep, who stopped snoring with his great gurgling snort, wriggled out from under them, and stood with laughing eyes and wagging tail, looking at them as they rolled and giggled among the pillows.