Holly Webb isn’t a pony book author as such: her two pony stories, Ponymagic (2010) and The Secret Pony (2007) are part of series full of other animals too. After a degree in Classics at Cambridge she worked as a children’s book editor before starting to write children’s books herself. Her books are aimed at the younger end of the market, and are full of magic and animals.
Finding the books
All in print.