Jumping Lessons (Book #2 in the Horseshoes/Kestrels Series) by Patricia Leitch

Sally now has her very own horse and she’s happier than she’s ever been. Then she and her friend Thalia begin jumping lessons, and everything changes. Thalia jumps her horse as if she were born to do it. Though she tries and tries, Sally can’t seem to get it right. Then Nick Ross, the world-famous show jumper, comes to town with his prizewinning mare who suddenly disappears. Sally is caught up in a mystery, an adventure, and a race against time.