A person i know is backing a horse and it's only 1 years old what should i do?

The others had some really good answers. There was a situation like this when I was a teenager and what we did is write an anonymous note and included a copied article of the importance of waiting til a certain age to back a horse. We didn't have internet back then, but now you could look up some articles and maybe print one off. Leave the note where the lady will find it and you could mention that you are reporting her to the proper authorities as well. This is if you don't want to do it in person. It might have the benefit of keeping this woman from getting defensive. I don't know. This kind of approach wouldn't work with everyone, but may be something you try second. But calling the authorities and the rescue is a great place to start. Good luck to you.