A horse called Darling by Delwynne Stephens

Puffin, 2010.Aussie Chomps. ISBN 978 0143304692.
When her beloved horse Manny, does not survive the waterhole jump which the girls attempt while out riding, Penny watches with despair as the vet puts the pony down. Her father, wanting her to get over this loss, finds another horse for her, one that has been neglected and left to its own devices for several years, a horse called Darling. With perseverance and pluck, Penny manages to pull the horse from its doldrums and get it ready for the events at the stables. Meanwhile Miranda with her expensive horse, Chanel, is out to win, thinking it is her turn. She has the added pressure of a father determined to make his daughter the best, and so she deliberately spooks Darling, knowing he will react badly to the sound of a whip. This involving story will appeal to middle school girls who are intrigued with stories of horses, but it is far more than that. In its pages are the themes of competition, of doing your best, of perseverance and tenacity, of competing fairly and forgiveness.
Fran Knight