Fighting Chance — Angela Dorsey

Chance and her best friend, Hanna, just want a relaxing ride for their first excursion with the very young Tubby, Chance's mare's foal, in tow. When they happen upon their mean school rivals, the ride instantly becomes unpleasant, but even that pales in comparison to what is to come. Hanna and Chance are separated, a tornado descends from the stormy sky, Tubby disappears, and then, unbelievably, everything becomes much worse!