There has been a lot of great advice here, pro and con, with most people being pretty reasonable in how they present it. Please consider the age of the OP, both in making either supportive or critical advice. It's not a crime to be 13 and feel that you have something to teach someone. She said she has spent her whole life around horses but only the last 3 years "learning about them". So, maybe she means that the lived near them or family who did, but now she is reading, learning from someone, watching videos, and , best of all, coming to YOU ALL for some learning. What an honor to be asked. Please treat your student with respect, even if you are saying "no".