Canterbury inquest officer, Constable Rob Stokes said a fencing contractor had partially erected a fence the day before, putting a strainer post either side of the paddock and a tension wire running between them.
The wire was left on the ground overnight. In some places, the wire was above the undulating ground.
"When Nicky saw it, she said, 'Athena, just watch out for the wire'," Fisher told the inquest.
Pellett's horse, Tiny, had "bizarrely" got the wire caught in its shoe, she said.
Fisher described how the wire was around the horse's leg and had caused her own horse to get "quite antsy".
She saw the hind quarters of Pellett's horse start going down and rushed to tie up her horse.
"It wasn't rearing. It was weird. When her horse started going down... you just panic, because you just know it's not going to be good," Fisher said.
When she looked back, her friend was lying on the ground.
"It all happened so very fast," she said. "It still sends shivers down my spine."
She yelled her friend's name but got no response. Running to her side, she found her unresponsive.
"She was snoring so I knew it was pretty bad."
Emergency services were called and Pellett was flown to Christchurch Hospital with serious head injuries. She never regained consciousness and died five days later.
Police and WorkSafe investigated.
Fisher said there were no signs saying they shouldn't be in that field on that day.
"If there was a sign saying, 'Don't enter', we wouldn't have," she said.
WorkSafe inspector Bridget Murray admitted today it was a "difficult" investigation under the "limitations" of the old Health and Safety in Employment Act 1992.
The replacement Health and Safety at Work Act 2015 has a more "modern approach", she said, which would have required the fencing contractor to communicate a site-specific safety plan with the sports club.
The inquest has been adjourned and will likely recommence in July.
