Beryl Bye wrote Christian devotional books, and her pony books are written from a Christian perspective. I have only read Pony for Sale, but this isn’t a book which wallops you around the head with its faith. I think it is a book written by an author whose way of life it genuinely expresses: yes, there is obviously some intent to persuade the reader to think about Christianity, but it’s done well.
Her three books are about the same three characters: Cathy, Belinda and Jane.
Finding the books
All the titles are easy to find, and generally reasonably priced.