The accident cost the lives of her younger sister and two boys after their canoe capsized. The boys' father is still missing, feared drowned.
Callie Mackay reached the shore with her father Garry, 36, after their Canadian-style canoe overturned in "sea like glass", throwing the party of six into the open loch at Gairloch in the west Highlands.
As the family mourned the loss of Callie's sister, Gracie, five, who died at the Yorkhill Royal Hospital for Sick Children in Glasgow yesterday, rescuers said the child's efforts had been remarkable.
The latest confirmed fatality took the death toll to three. Brothers Ewen and Jamie Beaton, aged five and two respectively, died in Raigmore Hospital in Inverness on Sunday, just hours after the incident.
Their father, Ewen Beaton, 32, from Beauly, Inverness-shire, who had been with his family on a day out with their friends the Mackays, is still missing.
Police said all the children had been wearing lifejackets, but it was unclear whether the adults had been.
Peter Godding, the senior coastguard officer co-ordinating the search, said he was astonished that Callie had managed to swim to shore to help raise the alarm, describing her as "very courageous and very resourceful".
"It's amazing really, she swam quite a long way in the sea, which is no mean feat. It's pretty incredible that she did survive, with the adult as well," he said.
Callie, who lives with her family in Muir of Ord, near Dingwall, was able to get help from locals close to the Sands Caravan Park overlooking the loch after Sunday's tragedy.
The six were near a stretch of water known as Caolas Beag when the craft, which they had brought with them, overturned. Callie and Mr Mackay reached the shore and her father went to a house about a mile away, where Jim Aaron lives.
Mr Aaron, 70, said: "He said he saw his mate go under and there were four kiddies bobbing about in the water. I got the coastguard then followed him back over about a mile away where he had come out.
"The father had left the girl about half the distance we were heading back. She had come out of the sea and was heading in the same track as him. He was very stressed.
"The girl wasn't too bad but I don't think she realised the full impact of the situation. She was cold and shivery."
James Cameron, 34, who runs the caravan site, was out in his boat when he heard of the accident. He and a friend managed to pull the five-year-old girl out of the water.
"We heard there was a girl missing. So we went out and actually found her. She was face down and unconscious. She had her buoyancy aid on. It was keeping her afloat but wasn't keeping her head out of the water."
He said when they got her on board they tried to resuscitate her but then the helicopter arrived to take her to hospital on Skye, from where she was transferred to Glasgow.
Other family members attended the scene yesterday along with a search and rescue helicopter, two lifeboats, Red Cross fast RIBs and coastguard personnel.
The canoe group had headed north towards Longa Island and then it is thought they went back towards the mainland at Rubha Ba, where there are caves.
Inspector Neil Mackinnon, area police commander, said inquiries were at an early stage.
Mr Godding added: "The Canadian-style canoe has no inherent buoyancy of its own and is quite an unstable canoe unless you are with people who are experienced. If you get a few people in them, they can be quite dangerous."