Tia Brown's seven-year-old pony called Helena suffered a catastrophic head injury following a fall on Saturday.
While the Fife schoolgirl was practising for a showjumping competition taking place the next day, she fell off which spooked Helena causing her to bolt.
As the horse was cantering off she slipped in a puddle, hit her head on a concrete post and died instantly.
Tia's mum Maggie told The Courier the freak accident had left the family heartbroken and Tia was unable to attend school for days.
She said: "Tia has been inconsolable since.
“It was heartbreaking to watch Tia laying in the puddle for over an hour with Helena stroking her and willing her to come back to her even though it was too late.
“As her mum, not being able to take away her devastation and that pain was just awful.
“Tia lived and breathed horses and loved Helena so much.
“When she wasn’t with her, she was talking about all the great plans and aspirations she had for them both.”
Maggie said her daughter’s dream had been to compete with Helena at a future Royal Highland Show.
She added: “Helena was a happy and healthy horse that had already won many rosettes with Tia on her back and everyone had high hopes.
“Horses and show jumping was everything to Tia, it has been her complete obsession since she was five-years-old.”
Tia had raised the money herself to buy Helena two years ago, but this time her mum has decided to help.
Maggie has launched a crowdfunding campaign in the hope of raising enough to get her daughter another horse.
She said: "Tia had done everything to raise the money to buy Helena two years ago and they were inseparable ever since.
“We just want to do what we can for Tia so she can fill this void and continue with her show jumping, reach her potential and realise her dreams with Helena always in her heart.
“We’ve been overwhelmed by the generosity heartfelt messages of support of those who have already made donations.”