Unicorns Don't Give Sleigh Rides: Adventures of the Bailey School Kids, Book 28

Liza is on her way to the local stables when she slips on the snow and hurts herself! Out of nowhere, a sleigh pulled by a white unicorn appears and takes her all the way to the stable. Her friends don't believe it was really a unicorn; Liza must have been seeing things! But Liza is determined to prove that she knows what she saw!