Three years is 1,095 days.

Consider what that means in terms of the accumulation of daily tasks: hunting, maintaining fire, maintaining shelter, managing food storage, finding water, managing the physical demands of cold and darkness, and doing all of this alone after the deaths of her companions.

Consider the number of nights spent alone on that island.

The winters — two or three of them — during which the days were very short, the cold was extreme, the island was surrounded by ice, and there was no ship that would be passing by to rescue her.

The springs that followed those winters, when the ice broke and the birds returned and the seal population appeared on the rocks, and she was still there.