JoAnne Chitwood Collier, (1955 - ) got her first horse when she was 12, for her birthday, and has had horses on and off ever since. When she wrote A Horse Called Mayonnaise, she had a black Morgan mare called Easter, and a Quarter horse mare named Wahkena. She has written a series of Christian pony books.
Finding the books:all are reasonably easy to find in the USA. None were published in the UK.