Who is She?

She walks through the desert,
Hot sand on her feet,
But still she keeps going,
Her life is no treat.

She walks through the city,
Not a penny to her name,
But still she keeps going,
This isn't a game.

She walks through the Arctic,
Slipping on ice,
But still she keeps going,
This is sacrifice.

She walks through the sky,
She ain't got a clue,
But she isn't going,
Cause her life is through.