The April 4 1929 edition of the Toronto Daily Star continues to be a useful source of material! Here’s a photograph of a 12-year-old British girl who had been successful at show jumping:
Searches didn’t reveal much about Olive Ricks. I found a photograph of her with, presumably, all of her prizes, and a photograph of her having her competitor’s number adjusted. I also found out that she eventually became Olive Evans. But I don’t know what happened to her; I guess she stopped competing when she got older. I suppose that 204 prizes is enough, really.