She was skiing at Treble Cone near Wanaka during a family holiday on July 14, when her last run of the day ended in disaster.
"I was enjoying a quiet run down the main slope, and did not hear any skiers or boarders behind me. The next thing I knew was someone knocked me over from behind. The man must have come over the brow of the hill at great speed, maybe just landing from a jump, since I had not heard him. I do not even know if he was skiing or boarding, it happened so suddenly," she said.
When she said she could not move, the skier went off to alert ski patrol, who arrived to carry her down the slope on a stretcher.
After medical assessment at the first-aid room, she was told it could take up to an hour to get a helicopter because it was so late in the afternoon, so instead she was taken by ambulance to the Wanaka Medical Centre, only to be transferred to Dunstan Hospital and onwards to Dunedin Hospital.
The doctor's prognosis was that it would take five to six months to heal. The accident also left her with a broken rib, as well as pain in her elbow and neck. Back home recovering, Ms Robertson, who has been skiing for 30 years, reflected on her ordeal.
"I am usually not one to complain, and I don't want to feel sorry for myself, but it is a very painful injury. Yet, I consider myself incredibly lucky it was my shoulder which took the impact and not my spine. If someone had hit me square in the back at that speed, I might not have survived," she said.
"I have for a moment considered dropping skiing altogether after this. But skiing has brought my family together for a common interest, and it is just so beautiful up there on the mountains. When I eventually go back to skiing next season, it will be with some apprehension."
Snowboarder Lauren Hawke, who lives in Queenstown and works as a bartender, considers herself fortunate to be able to go back to the slopes later in the season after a knee injury she suffered three weeks ago.
She had overstretched her knee slightly while boarding at Coronet Peak. When she went back to boarding the following weekend at the Remarkables, the minor injury turned into a major complication when she had a bad landing from a jump in the terrain park.
The result was a torn cartilage, which cost her 10 days off work. She has since returned to work, but is only able to work part-time as her bar-tending jobs require her to stand for more hours than her recovering knee can bear.
"It is endlessly frustrating because I live here in Queenstown and work in hospitality mainly so that I can spend my days snowboarding."
The experienced snowboarder is already well on her way to recovery through intensive physiotherapy, with two weekly sessions and gym training in between.
"Lauren has been progressing really well. If she keeps up the good work, she could be back on the snow in about another three weeks," physiotherapist Louise Parker from The Studio in Queenstown said.
She said there were two important ways to prevent injuries.
"First of all, make sure you are as fit and strong as possible, as strong muscles help stabilise the joints. Secondly, make sure your bindings are accurately adjusted by a qualified technician. Research shows knee injuries are very often caused by faulty bindings," Ms Parker said.