The Outside of a Horse

A girl's dad comes home from the war with a leg missing. She wants a horse but her dad can't afford one.

From Amazon:

Hannah, 13, has always loved watching horse races on television with her father, but when she begins to help out at a local riding stable, she discovers how much more she enjoys working with real animals, especially those who have suffered abuse.

She particularly loves a filly named Rega, the offspring of a Premarin mare (a pregnant horse from which urine is collected to make pharmaceuticals).

When her dad returns from Iraq as an amputee suffering from post-traumatic stress disorder, Hannah's work at the stable not only helps her cope with the problems at home, but also leads her to equine-assisted psychotherapy and riding therapy for her troubled father.