The Greening of Whitney Brown
I saw this! It's a cute movie about a girl from the city (Prissy) moving to a farm where she meet an adorable and funny Clydesdale, Bob.
Whitney Brown, a spoiled pre-teen from Philadelphia, is forced to move to the country when her parents feel the squeeze of economic hard times.
A fish out of water, far from her comfort zone, she befriends an amazing horse, and undertakes a misguided journey back to her old life, only to discover that her family is her home.