Ponies of Chincoteague #4 Moonlight mile / Catherine Hapka.

"When her horse show performance goes horribly wrong, Nina wonders if a Halloween ghost could be involved in this fourth book in a contemporary middle grade series in the tradition of Marguerite Henry's Misty of Chincoteague. Nina Peralt's boarding and lesson barn will be putting on a horse show this fall, and she can't wait to show off how well she and her pony, Breezy, have been doing lately! Bonus: the cute older brother of one of her fellow riders will be helping out as jump crew. Unfortunately, once the show starts, everything goes wrong for Nina in the most embarrassing ways possible. Could something supernatural be to blame? New Orleans is always a little spooky around Halloween, but this year Nina slowly becomes convinced she's being haunted by the ghost of an angry ancestor. Can her Pony Post pals help her banish her fears and live down her terrible show day?"--Jacket.