Pony boy story.

[MummifiedDuck]

Looking for a story about a man tricked into being the pony boy for a woman going to school. She was from a rich family and he had always had a crush on her. The person who was supposed to be her pony backed out, leaving her in the lurch. She's crying, he feels sorry for her, and thinks this is a way to get close; she promises him the best treatment. When they get to school, she begins to treat him without compassion.