That Horse Whiskey

Disappointed when her father cannot fulfill his promise of buying her a horse for her thirteenth birthday, Lainey throws her energy into training a neighbor's cantankerous horse, with whom she soon falls in love.

From Amazon:

When Lainey doesn't get the horse Dad promised her for her 13th birthday, she goes to work at the local stable where her task is to train an obstreperous horse as well as a city boy named Ryan.

If Lainey can teach Ryan and also get the horse, Whiskey, to carry his riders more than a quarter of a mile from the corral, she'll show her father how strong a girl she is. She'll also get something else she wants.