Friendly Foal, Winnie the Horse Gentler Series by Dandi Daley Mackall and published by Tyndale House.
"Stay right where you are! I'll explain everything when I get there! I need you desperately, Winnie Willis!" Nobody has ever needed Winnie before. But she already has a big problem of her own. The newborn foal has lost her mother, and the world doesn't look friendly. Winnie knows how the filly feels. It's been two years since Winnie lost her mom, and she still has trouble trusting humans. So why should the foal trust her? But time is running out. Then Sal, a classmate, arrives with a little surprise - and a lesson about friendship that Winnie will never forget. Recommended for ages 8 to 12.