Iona Sclater, 15, died after the fall in Abington Pigotts, Cambridgeshire, on Sunday morning.
She was one of the sport’s brightest prodigies, and was set to take part in the 2019 European eventing championships in Poland.
Only five days before her death, she dedicated an Instagram post to Swatchy.
She wrote: “Find me someone who looks at me the way Swatchy does.
“Thank you @adamfanthorpe for capturing these special moments.”
“Iona was the kindest, most thoughtful person ever. She would always pick people up when they were down and enjoyed every moment with everyone”
It drew more than 8,000 likes, but has been the source of agonising tributes.
One wrote: “Rest in peace. My condolences goes out to the family and friends. So sorry for your loss.”
Parents Charles and Hetty, along with Lara and Alicia, have been left devastated by the tragedy.
A pal wrote: “Iona was the kindest, most thoughtful person ever. She would always pick people up when they were down and enjoyed every moment with everyone.
“Iona you are a legend and we will love you forever. Another angel gone too soon.”
A British Eventing statement read: “British Eventing was devastated to receive the news that one of our young members and bright stars in the sport, Iona Sclater, sadly died in a riding accident at home on Sunday 11 August.
“Our thoughts are with Iona’s friends and family at this very difficult time.
“Iona was an exceptionally talented and dedicated young event rider.”