Ann Wigley wrote her first book The Red Horse Haunting, for the J A Allen Junior Equestrian Library. She helped with the local Pony Club and ran a livery yard, and wrote the story while recovering from an operation. She only sent it to the publisher because her daughter insisted! Since then, she has written a story for the American Pony Club publishers. This is a good read: the only odd thing about it is something presumably visited on it by the publisher. The story is set in England but has odd Americanisations, presumaby to make it more acceptable to its target audience.
Finding the books: generally easy to find, and not too expensive.
The Red Horse Haunting
J A Allen, 1991
Rachel’s family move to a lovely thatched cottage, with a paddock, and stables in
need of repair. However, odd things soon start happening, and Rachel and her horse
Red Flame both feel the fear that inhabits the old stables.
Tears for a Tall Horse
Pony Club, Stabenfeldt, 2004
Short story: Pony Island
In: A Treasury of Pony Stories, Kingfisher, 1996